Wildfires hit U.S. West, could spread to Native American sites LOS ANGELES (Reuters) - Wildfires, including one that could extend to Native American archaeological sites in New Mexico, raged across the western United States on Monday as dry weather and gusty winds stymied firefighters' efforts to make headway against the flames. In Southern California, a fast-growing wildfire spread to 30,000 acres, expanding by 50 percent from Sunday to Monday. It has destroyed six homes since it broke out last Thursday. In New Mexico two smaller fires roared out of control in separate wilderness areas. Firefighters warned that one of them could gain strength during the windy, dry afternoon as it consumed pine trees in its path. That blaze, the Thompson Ridge fire, changed direction overnight and now could spread to Native American archaeological sites in the Valles Caldera National Preserve, U.S. Forest Service spokeswoman Dana Howlett said. The sites include six volcanic mounds important to the Pueblo of Zia indigenous group. The blaze threatened the communities of Compton Valley, Rancho de la Cueva and Elk Valley, Howlett said. About 50 families were evacuated on Friday and remained out of their homes. "With the intense heat, the fire gets more intense and you often have trees that are torching, and when that happens, large smoke plumes start going up," Howlett said, adding that from a distance the flames and smoke can make it seem like a volcano is erupting. Separately, the Tres Lagunas fire in New Mexico's Pecos Wilderness has charred nearly 8,000 acres and was only 5-percent contained, said Fire Information Officer Dick Fleishman. The Southern California blaze, dubbed the Powerhouse fire, grew by some 10,000 acres on Sunday and overnight into Monday, U.S. Forest Service officer Ronald Ashdale said. The blaze, in the far northern part of Los Angeles County, was 40-percent contained by Monday morning, he said, and a change in its direction meant the number of homes threatened had dropped to 400 from 1,000. Late Monday afternoon, most the roughly 2,000 residents who had been evacuated were allowed to return home, said Matt Corelli, a spokesman for the U.S. Forest Service. Evacuations also were ordered in the town of Valley Springs in the California gold country. Despite cooler, wetter weather that moved in overnight, firefighters say it will take until next Monday to contain the blaze, Ashdale said. For the first time in decades, the Forest Service is using night-flying helicopters to drop water on the flames. In Colorado, a wildfire that erupted in the foothills west of Denver on Monday has prompted mandatory evacuations of homes within a 4-mile (6.5-km) radius of the blaze, fire officials said. The cause of the fire was under investigation and there was no estimate of its size, said Jefferson County Sheriff's Office spokeswoman Jacki Kelley. In Alaska, a lightning-sparked fire in the Denali National Park and Preserve had spread across 950 acres of mostly tussock and brush, among ponds still partly covered with ice, park officials said. The fire broke out shortly after snowmelt and before green shoots had time to appear, leaving dry brush that is easily ignited, said park fire management officer Larry Weddle. The Denali fire is unusual because it is at relatively high elevation, about 2,700 feet, Weddle said, adding that it is in a remote area and poses no immediate threat to property or people. A 2,300-acre (930-hectare) fire near Tok in eastern Alaska was threatening the Alaska Highway, but so far no roads have been closed, officials said. Reporting by Sharon Bernstein in Los Angeles, Zeie Pollon in Santa Fe, Keith Coffman in Denver, and Yareth Rosen in Anchorage; Writing by Sharon Bernstein; Editing by Cynthia Johnston, Gary Hill and Xavier Briand