CONIFER, Colo. -- The Black Mountain Fire is now believed to have started from an earlier lighting strike that smoldered, officials said Tuesday.

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The fire burned about 250 acres northwest of Conifer and was 40 to 50 percent contained by Tuesday morning.

Four air tankers, a single-engine tanker and two helicopters were working the fire Tuesday after a busy day on Monday.

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On Monday, the air strikes resulted in 105,000 gallons of water being dropped on the fire, aided by 22 retardant drops.

Firefighters were warned there was a good chance for strong southwesterly winds Wednesday. About 270 firefighters are working on the stubborn fire.

The blaze was within one-quarter mile of at least one house and within 2 miles of subdivisions in the area, about 25 miles southwest of Denver.

Four subdivisions were still evacuated on Tuesday. They were: - Brook Forest Estates, Alpine Hills, Secluded Acres and Carol Lane. Residents from other subdivisions that had been evacuated Sunday were allowed to return Monday night.

In all, more than 2,400 residences were evacuated during the height of the fire. All were within a 2-mile radius of the forest fire.

Officials said the fire could be fully contained by Wednesday, if the winds cooperate and no other major fires flare up.

Also Monday, grass fires outside Colorado Springs burned more than 6,000 acres and caused the Colorado Springs Airport to adjust flight patterns to avoid thick plumes of smoke. The fires also closed roads, threatened structures and forced the evacuation of some farm animals.

El Paso County spokeswoman Lt. Melissa Hartman said the blaze was contained in about three hours.

After a dry winter, more than 400 wildfires have burned about 15,600 acres in Colorado this year, according to the Rocky Mountain Area Coordinating Center of the National Interagency Fire Center.

In New Mexico, meanwhile, a fast-moving wildfire in the Santa Fe National Forest burned up to 700 acres within several hours Monday. Residents in the Dalton and Pecos canyons were asked to leave, fire information officer Claudia Standish said. Several campgrounds and about 400 homes are in the area, state police said.

Erratic winds fanned the flames, sending thick billowing clouds of gray smoke into the sky about 15 miles east of Santa Fe.

Fire information officer Christa Orozco said the fire was caused by humans, but the exact cause was not known.

In another New Mexico blaze, fire lines had been established around 65 percent of a 15,000-acre blaze near Mayhill. The fire had destroyed 13 homes, 27 garages or other buildings, and five vehicles, officials said.

It was started accidentally last week by a man who later committed suicide.