* Fires among biggest in both states' history
* Containment lines cut around 10 pct of Colorado fire
* Lines extended around 35 pct of New Mexico fire (Updates status of Colorado fire, adds regional fire figures)
By Zelie Pollon and Keith Coffman
June 12 (Reuters) - Fire crews battling flames roaring through national forests in New Mexico and Colorado have made some progress beating back the blazes that have driven thousands from their homes and destroyed hundreds of dwellings, the authorities said on Tuesday.
The larger of the two blazes, now ranked as the third biggest on record in Colorado, has killed a woman whose remains were found in the ashes of a cabin where she lived alone on the edge of the Roosevelt National Forest, officials said on Monday.
Linda Steadman, 62, was the first casualty of the so-called High Park Fire, which has scorched more than 43,000 acres near the Wyoming border since it was ignited by lightning late Friday or early Saturday, and the fourth fatality in a Colorado wildfire this year.
Over 100 structures, including an undetermined number of homes, have been destroyed, and hundreds more dwellings - home to roughly 2,000 people - remain threatened by the blaze and are under evacuation orders, Larimer County officials said.
But authorities on Tuesday night reported making some headway against the flames, saying ground crews had managed to cut containment lines around 10 percent of the fire's perimeter. Residents from a couple of neighborhoods would be allowed back into their homes Tuesday afternoon, they added.
Still, federal incident commander Bill Hahnenberg said he anticipated firefighters would be battling the blaze for several weeks, if not into the fall. The plan for Tuesday, he said, was to focus on the southern edge of the fire with a heavy aerial assault to safeguard populated areas.
About 500 firefighters were on the scene on Tuesday, but Hahnenberg said he expected that number to climb to as many as 800 in the days ahead.
"SMOKEY BEAR" FIRE SITE
Hundreds of miles to the south, firefighters also turned a corner against a wildfire burning in the rugged Lincoln National Forest in central New Mexico, where some 37,000 acres of mixed conifer have gone up in flames.
By Tuesday night, fire crews had extended containment lines around 35 percent of the perimeter of the Little Bear Fire, helped by calmer winds and higher humidity, officials said.
Damage-assessment teams reaching the fire zone for the first time on Tuesday determined that 224 homes and 10 outbuildings had been destroyed. Previously, it had been estimated that 35 structures had been burnt down.
Nine residential areas - which are home to up to 2,500 people - remain evacuated, while the resort village of Ruidoso, a town of some 9,000 year-round residents, is still under threat, said Kerry Gladden, a Ruidoso information officer.
"Our strategies for the day are to strengthen the containment lines, (and) build new bulldozer lines on the side leading down to Ruidoso. We're hitting heavy this morning with air tankers," Gladden said.
Governor Susana Martinez declared a state of emergency in Lincoln County on Tuesday, releasing additional state funds for fire relief.
Nearly 1,000 personnel have been assigned to the Little Bear Fire, including 400 National Guardsmen sent by the governor to help evacuate residents and protect property.
The blaze was sparked by lightning on June 4 and was largely brought under control within days, but high winds blew flames past containment lines last week, giving the fire a second life.
The fire is in the same area where firefighters in 1944 rescued the orphaned bear cub later dubbed "Smokey Bear," the basis for a cartoon character who symbolized the U.S. Forest Service and was famed for the slogan, "Only you can prevent forest fires."
In southwestern New Mexico, the separate Whitewater-Baldy Complex fire, the largest in state history, was 37 percent contained after blackening 278,708 acres. (Writing by Steve Gorman; Editing by Cynthia Osterman and Andrew Osborn)