Raging wildfires forced hundreds of residents to flee homes in Colorado and New Mexico on Sunday as high winds and high temperatures fanned the flames, authorities said.

One of the fires was burning out of control in a part of New Mexico where firefighters found an orphaned cub who became "Smokey Bear," a symbol of the U.S. Forest Service, almost 70 years ago.

Colorado's High Park Fire, about 15 miles northwest of Fort Collins, was burning out of control and had scorched an estimated 20,000 acres, Larimer County Sheriff Justin Smith said. The fire continues to grow, he said.

Hundreds of residents were under mandatory evacuation orders, and authorities closed several camping areas in the Roosevelt National Forest.

Fueling the fire in Colorado were temperatures rising above 90 Fahrenheit(32 Celsius).

"The stiff winds and dry conditions make this very, very tough" to fight, Colorado Governor John Hickenlooper told a news conference.

Smith said the blaze had destroyed about 18 buildings, and one person was missing within the fire zone.

An 80-mile-long plume of smoke was visible across northeastern Colorado and in Wyoming. The sheriff said firefighters believed the blaze was started Friday night by lightning.

In central New Mexico, about 1,500 people fled the "Little Bear" fire near the resort community of Ruidoso to shelters set up by churches and the Red Cross.

The fire, ignited by lightning last Monday, had grown to 28,000 acres as of Sunday and had burned 36 structures, Kerry Gladden, a spokeswoman for the village of Ruidoso, said.

Firefighters had not managed to contain any portion of the blaze, which was burning in an area where in 1944 firefighters rescued a black bear cub orphaned by a wildfire. The cub was nursed to health and became "Smokey Bear," the symbol for the well-known U.S. Forest Service public education campaign with the slogan, "Only you can prevent wildfires."

About 100 National Guard troops joined 300 firefighters to fight the fire in the steep, rocky and often inaccessible White Mountain Wilderness of the Lincoln National Forest, officials said. Much of the firefighting was done from the air with five air tankers and at least eight helicopters.

Conditions remained severe, "with high temperatures, high winds and low humidity," said Tom Schafer, a spokesman for the Forest Service.

In southwest New Mexico, meanwhile, containment lines were holding around the state's largest wildfire ever, the 278,039-acre White Water Baldy blaze, which was not threatening any populated areas, said Forest Service spokesman Gerry Perry.

Perry said the blaze was about one-third contained.

"We're in pretty good shape now," he said.