LOS ANGELES -- Three people were killed Monday when a plane fighting one of the many wildfires plaguing the western United States crashed in a ball of flame near the California-Nevada border, officials said.

"The aircraft crashed in abnormal circumstances and it's under investigation," Jerry Johnston of the Federal Aviation Administration told AFP.

None of the three people on board the CI-30 air tanker survived, Johnston said, adding that the plane was under contract with the U.S. Forest Service to help fight a fire that has engulfed more than 2,500 hectares (6,000 acres) on the California-Nevada border.

Some 200 houses are at risk from the flames, and hundreds of people have been evacuated from their homes around the California town of Walker, where two houses have already succumbed to the fire.

The wildfire, one of several currently raging in the western United States, broke out on Saturday, and heavy winds in the area have made it difficult to control.

Thousands of hectares (acres) of forest are lost to wildfires in the western United States each summer, as the woods are made vulnerable by a combination of drought and high winds.

This year, however -- one of the driest in decades -- the wildfire season began earlier than usual.

The state of Colorado is now battling its worst wildfire ever, which has scorched some 40,000 hectares (99,000 acres) of land and destroyed some 22 homes, forcing 5,400 people to leave their homes as the flames grow dangerously close to the populous city of Denver.