DENVER — A major spring snowstorm dumped more than a foot of snow across the Colorado-Wyoming state line on Thursday, canceling hundreds of flights, shutting down schools and making roads treacherous.
At least 15 people were treated at Cheyenne Regional Medical Center for injuries from three pileups involving about 50 vehicles on Interstate 25 just south of the state line, hospital spokeswoman Leslie Cook said. Authorities initially reported at least 33 were injured, but hospital officials said some turned out to be uninjured or refused treatment.
The crashes led Colorado officials to close more than 40 miles of the road south of Cheyenne and a 45-mile stretch between Pueblo and Walsenburg. The highway is the main north-south thoroughfare in Colorado.
A 20-mile section of U.S. 50 between Pueblo and Penrose reopened Thursday evening.
Aaron Fowler, chief of Laramie County Fire District 1 in Wyoming, said many other vehicles slid off the road while trying to avoid the wrecks.
"Visibility when I arrived on the scene was, I would say, 100 yards _ very high winds and blizzard conditions," Fowler said.
Winds were gusting to nearly 40 mph in Denver, about 100 miles south of Cheyenne. The Regional Transportation District, the Denver-area mass-transit service, pulled its buses off the roads in Longmont, Colo., 30 miles north of Denver because of whiteout conditions.
"I saw three flipped cars," said Zachary Whitaker, who spent four hours driving his grandmother to the Denver airport from Gering, Neb. "Five more run off the road. Cars in ditches all over."
The Red Cross opened six shelters for stranded motorists.
The state's eastern half remained under a blizzard warning Thursday while Denver and most of the state was under a winter storm warning. Gov. Bill Ritter declared a state of emergency and activated the National Guard, though its mission was not immediately disclosed.
Forecasters predicted up to 2 feet of snow south and east of Denver by Friday and up to 15 inches in the city itself. More than a foot of snow was expected in the foothills west of Denver.
At Denver International Airport, Frontier Airlines canceled 54 flights and its Lynx commuter affiliate canceled 33, spokesman Steve Snyder said. Southwest Airlines canceled at least 82 flights and American Airlines canceled 26.
Dozens of school districts called off classes Thursday, although many already were closed for spring break. The University of Colorado in Boulder and Colorado State University in Fort Collins shut down early.
At the state Capitol, both the House and the Senate shut down early, as did state and federal courts and the Denver Zoo.
The storm was welcome news to some after a dry winter marked by repeated brush fires and fire warnings.
"It may disrupt some guys who were in the field planting," said Shawn Martini, a spokesman for the Colorado Farm Bureau. "But at this point, they can delay that because the water is more important."
Gruver reported from Cheyenne, Wyo. Associated Press writers Steven K. Paulson, Colleen Slevin, Don Mitchell and Alysia Patterson in Denver also contributed to this report.