SAGUACHE, Colo. -- A helicopter fighting a fire in southwestern Colorado crashed Monday afternoon, injuring four people, authorities said.

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The Bell 206 helicopter was making an initial attack on a wildfire about 15 miles west of Saguache when it crashed at about 4:30 p.m., said Larry Helmerick, a fire information officer with the Rocky Mountain Coordination Center.

Four people on board were injured in the crash, Helmerick said.

Two people had minor injuries and were taken to Alamosa hospitals. Two others were airlifted to Pueblo and Colorado Springs hospitals.

The extent of their injuries and their identities are unknown.

The helicopter was fighting a new wildfire called the Trickle Fire about 130 miles southwest of Denver. Helmerick said that the fire was small -- less than acre.

Only local firefighters, a single-engine tanker and the chopper were involved in tackling the blaze.

Investigators from the National Transportation Safety Board and a team from the National Interagency Fire Center in Boise, Idaho, were en route to the site.

The crash comes less than a month after a helicopter crashed July 30 while fighting the Big Elk fire southeast of Estes Park. Pilot Gordon Knight, 52, of Boulder, was killed.

He was at least the 15th person killed this summer while fighting or en route to fighting wildfires that have burned millions of acres in the West.

Two weeks before that, a PB4Y-2 Privateer broke apart while battling the Big Elk fire, killing Milt Stollak, 56, of Cathedral City, Calif., and Rick Schwartz, 39, of Ulm, Mont.

NTSB investigators and a U.S. Forest Service team were on their way to Fairplay, in the mountains southwest of Denver, where a twin-engine Beechcraft Baron on a reconnaissance flight for the Forest Service made an emergency landing Monday. The two people on board were not injured, Helmerick said.

The plane was forced down after engine problems, he said.