The contract plane went down 14 miles north of St. George about 6 p.m., said Bureau of Land Management spokesman Wendell Peacock.
The pilot's name had not yet been released and the cause of the crash still was being investigated.
The pilot had just dumped a load of retardant when his plane either stalled or pitched, said Dammeron Valley resident Andrew Tomer, who saw the accident.
Within a few seconds the plane crashed and burned. Within a few minutes, a helicopter and plane made drops on the fire started from the crashed aircraft, Tomer told The Spectrum.
The plane was not one of the old, heavy, multiengine air tankers that the government has grounded out of safety concerns.
The single-engine tankers are basically crop dusters retrofitted to drop water, retardant or seed, Peacock said.
The other aircraft assisting in the fire were grounded, according to procedure, spokesman David Eaker said. He did not know if they would be back in use Friday.
Bureau of Land Management spokesman David Boyd said the major, south portion of the Dammeron Complex fire, had burned about 3,600 acres and had not spread much since Thursday morning. It was expected to be contained by Saturday.
It was fought by firefighters from federal, state, and municipal agencies, aided by two air tankers, including the one that crashed and two helicopters.
Earlier Thursday, residents from two dozen homes north of St. George at Brookside were allowed back to their homes after being evacuated Wednesday when the northern portion of the Dammeron Complex fires burned close to their homes. That part of the blaze was contained Thursday after burning about 60 acres.
The fires were started Wednesday by lightning.
Another fire, about 10 miles west of St. George, the Utah Hill fire, was contained Wednesday after burning approximately 630 acres.
The Federal Emergency Management Agency said it had approved a fire management grant that will cover 75 percent of the local and state firefighting costs for the fires.
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