YOSEMITE NATIONAL PARK, Calif. — Dense smoke from a wildfire burning in and around Yosemite National Park on Saturday hampered both suppression efforts and the prized views sought by holiday weekend tourists.

For the first time since the blaze broke out in a neighboring forest two weeks ago, smoke obscured Yosemite Valley, home to the park's most popular landmarks, spokeswoman Kari Cobb said.

"I'm in Yosemite Valley right now, and I cannot see the cliffs around me," Cobb said. "The wind has shifted and smoke is impacting the entire park. We have been lucky until now."

All the campgrounds in the Valley still were full as of Saturday morning, despite the thick blanket and burning smell that permeated the area and was expected to linger until at least Monday, she said.

As a health precaution, visitors were being asked to scale back their outdoor recreation plans and avoid strenuous activities or even stay indoors.

Meanwhile, firefighting aircraft were grounded most of the morning because of low visibility caused by the smoke, U.S. Forest Service spokesman Mark Healey said. The blaze had scorched 343 square miles of brush, oaks and pines and 11 homes, as of Saturday, an area larger than the cities of San Francisco, Oakland and San Jose combined.

Of that total, 94 square miles of wilderness have burned in the northern section of Yosemite, up from 75 square miles a day earlier.

Although containment efforts proceeded on a positive note overnight, officials were concerned Saturday about a 150-acre spot fire that crossed a road and prompted an evacuation order for homes near the west entrance of Yosemite, Healey said.

Once planes and water-dropping helicopters were cleared to take off again, the worry lifted some along with the evacuation order.

"Air operations are going full-blast to bring this fire under control," Healey said late Saturday afternoon.

The cause of the fire, which started and has claimed the most acreage in the Stanislaus National Forest, is under investigation.

Healey said fresh firefighters were being brought in to replace tired crews, but that officials did not plan to reduce the nearly 5,000 people assigned to the blaze.

The wildfire is the largest now burning in the United States and is the fifth-largest in California history.

Earlier on HuffPost:

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  • Firefighters enter a grove of giant sequoias in Yosemite National Park in this photo made on Sunday, Aug. 25, 2013, and released by the National Park Service on Tuesday. (AP Photo/National Park Service)

  • AP10ThingsToSee - Inmate firefighters walk along state Highway 120 as firefighters continue to battle the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong, File)

  • The Rim Fire burns through trees near Yosemite National Park, Calif., on Tuesday, Aug. 27, 2013. (AP Photo/Jae C. Hong)

  • Russell Mitchell

    Firefighter Russell Mitchell, left, monitors a back burn during the Rim Fire near Yosemite National Park, Calif., on Tuesday, Aug. 27, 2013. (AP Photo/Jae C. Hong)

  • The Rim Fire burns through trees near Yosemite National Park, Calif., on Tuesday, Aug. 27, 2013. (AP Photo/Jae C. Hong)

  • A videographer records the Rim Fire burning through trees near Yosemite National Park, Calif., on Tuesday, Aug. 27, 2013. (AP Photo/Jae C. Hong)

  • A smoke plume from the Rim Fire rises nera Yosemite National Park, Calif., on Monday, Aug. 26, 2013. (AP Photo/Jae C. Hong)

  • A helicopter reloads fire retardant as firefighters continue to battle the Rim Fire in Tuolumne City, Calif., on Monday, Aug. 26, 2013. (AP Photo/Jae C. Hong)

  • Aerial Water Drop on Rim Fire

    In this Thursday, Aug. 22, 2013 photo provided by the California Army National Guard on Monday, Aug. 26, 2013, Sgt. Chris Boni, crew chief from the 1-140th Aviation Battalion (Air Assault) from Los Alamitos Joint Training Base (JFTB), releases water to help control the Rim fire below near Yosemite National Park, Calif. The The UH-60 Black Hawk Crews are battling the Rim wildfire, one of the largest in California history, in support of the U.S. Forest Service and CAL FIRE. (AP Photo/U.S. California Air National Guard, Master Sgt. Julie Avey)

  • In this Thursday, Aug. 22, 2013 photo provided by the California Army National Guard on Monday, Aug. 26, 2013, Sgt. Chris Boni, crew chief from the 1-140th Aviation Battalion (Air Assault) from Los Alamitos Joint Training Base (JFTB), releases water to help control the Rim fire below near Yosemite National Park, Calif. The The UH-60 Black Hawk Crews are battling the Rim wildfire, one of the largest in California history, in support of the U.S. Forest Service and CAL FIRE. (AP Photo/U.S. California Air National Guard, Master Sgt. Julie Avey)

  • Smoke clouds and bands of haze from the Rim Fire in the western Sierra Nevada loom up some 20 miles behind the famed granite monolith known as Half Dome, right center, seen from 11,500-foot Mt. Clark in Yosemite Valley in Yosemite National Park, Calif., Saturday, Aug. 24, 2013. (AP Photo/Tami Abdollah)

  • A fire truck drives past burning trees as firefighters continue to battle the Rim Fire near Yosemite National Park, Calif., on Monday, Aug. 26, 2013. (AP Photo/Jae C. Hong)

  • A burned SUV sits in front of a campground destroyed by the Rim Fire near Yosemite National Park, Calif., on Monday, Aug. 26, 2013. (AP Photo/Jae C. Hong)

  • A helicopter drops water over a hot spot while battling the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong)

  • A.J. Tevis

    Firefighter A.J. Tevis watches the flames of the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong)

  • The Rim Fire burns along Highway 120 near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong)

  • The Rim Fire burns along Highway 120 near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong)

  • A smoke rises from smoldering trees as firefighters continue to battle the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong)

  • Firefighter Charlie Ferris, of Los Angeles, watches a smoke plume from the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong)

  • A firefighter watches for spot fires during a burnout operation while battling the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong)

  • Inmate firefighters walk along Highway 120 after a burnout operation as firefighters continue to battle the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. (AP Photo/Jae C. Hong)

  • The smoke generated by the Rim Fire rises under a star-filled sky near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. Fire crews are clearing brush and setting sprinklers to protect two groves of giant sequoias as a massive week-old wildfire rages along the remote northwest edge of Yosemite National Park. (AP Photo/Jae C. Hong)

  • GROVELAND, CA - AUGUST 28: Cows graze in a field as the Rim Fire burns in nearby hills on August 28, 2013 near Groveland, California. Over 3,500 firefighters are battling the destructive Rim Fire that has charred 180,000 acres and has entered a section of Yosemite National Park. The fire is currently 23 percent contained. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 28: A CalTrans worker takes a break during a tree cutting operation in an area that was burned by the Rim Fire during a media tour of the fire area on August 28, 2013 near Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 25: A burned car sits on the side of the road after being consumed by the Rim Fire on August 25, 2013 near Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • YOSEMITE NATIONAL PARK, CA - AUGUST 25: Trees burned by the Rim Fire stand on August 25, 2013 in Yosemite National Park, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 25: Flames from the Rim Fire consume trees on August 25, 2013 near Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 25: U.S. Fish and Wildlife Service firefighter Corey Adams sits on a tree stump as he monitors the Rim Fire on August 25, 2013 near Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 24: West Stanislaus County Fire firefighters monitor the Rim Fire along highway 120 on August 24, 2013 near Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 24: A firefighter uses a hose to douse the flames of the Rim Fire on August 24, 2013 near Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • YOSEMITE NATIONAL PARK, CA - AUGUST 24: Smoke from the Rim Fire lingers over the O'Shaughnessy Dam at Hetch Hetchy Reservoir on August 24, 2013 in Yosemite National Park, California. (Photo by Justin Sullivan/Getty Images)

  • YOSEMITE NATIONAL PARK, CA - AUGUST 24: U.S. Forest Service firefighter Chris Brossard monitors a spot fire while battling the Rim Fire on August 24, 2013 in Yosemite National Park, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 25: Flames from the Rim Fire consume trees on August 25, 2013 near Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • YOSEMITE NATIONAL PARK, CA - AUGUST 24: A firefighter uses a hose to douse a spot fire while battling the Rim Fire on August 24, 2013 in Yosemite National Park, California. (Photo by Justin Sullivan/Getty Images)

  • In this undated photo provided by the U.S. Forest Service, the Rim Fire burns near Yosemite National Park, Calif. (AP Photo/U.S. Forest Service)

  • GROVELAND, CA - AUGUST 22: A firefighter from Central Calaveras Fire monitors the Rim Fire on August 22, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • YOSEMITE NATIONAL PARK, CA - AUGUST 22: Smoke from the Rim Fire is visible near the Hetch Hetchy reservoir on August 22, 2013 in Yosemite National Park, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 22: A firefighting helicopter flies in front of a plume of smoke from the Rim Fire on August 22, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • In this undated photo provided by the U.S. Forest Service, the Rim Fire burns near Groveland Ranger Station in Groveland, Calif. (AP Photo/U.S. Forest Service)

  • GROVELAND, CA - AUGUST 22: Firefighters from the Colorado based South Arkansas Fire District monitor the Rim Fire on August 22, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 22: Firefighters monitor a plume of smoke from the Rim Fire on August 22, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 22: A U.S. Forest Service firefighter monitors a radio while battling the Rim Fire on August 22, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 22: A firefighter from the Kern County Rio Bravo Hotshots looks for flying embers while battling the Rim Fire on August 22, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 22: Firefighters douse hot spots while battling the Rim Fire on August 22, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 21: Firefighters from Ebbetts Pass Fire District monitor a back fire as they battle the Rim Fire on August 21, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 21: A firefighter from Ebbetts Pass Fire District uses a drip torch to light a back fire as they battle the Rim Fire on August 21, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 21: Firefighters from Ebbetts Pass Fire District monitor a back fire as they battle the Rim Fire on August 21, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 21: A firefighter from Ebbetts Pass Fire District monitors a back fire as he battles the Rim Fire on August 21, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 21: Firefighters from Ebbetts Pass Fire District monitor a back fire as they battle the Rim Fire on August 21, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • GROVELAND, CA - AUGUST 21: A firefighter from Ebbetts Pass Fire District uses a drip torch to light a back fire while battling the Rim Fire on August 21, 2013 in Groveland, California. (Photo by Justin Sullivan/Getty Images)

  • BUCK MEADOWS, CA - AUGUST 21: Fire consumes trees along US highway 120 as the Rim Fire burns out of control on August 21, 2013 in Buck Meadows, California. (Photo by Justin Sullivan/Getty Images)