The rocket propellant that burned Monday afternoon at Hill Air Force Base produced a large cloud of toxic smoke and gas, base environmental officials said Tuesday, but the cloud dissipated rapidly and no reports have been received of personal injury.

The 40,000 pounds of Minuteman I missile solid fuel that ignited about 1:30 p.m. would have produced about 8,000 pounds of hydrogen chloride, released as gas and fumes, said Lt. Col. Phil Brown, the HAFB environmental safety engineer.Brown said the cloud rose to about 1,000 feet over the munitions igloo where the fuel was burning, but drifted south over the base on the prevailing wind and dissipated.

Area hospitals were notified about possible respiratory complaints, Brown said, but none were reported either on or off base.

A crew from the 2701st Explosives Ordinance Disposal squadron sent a remote-COntrolled robot equipped with a video camera and chemical sensors into the igloo Tuesday to determine if the fire was out and the extent of damage and possible chemical contamination inside the structure.

Maj. Doug Murray, commander of the 2701st, said the robot is equipped with a television camera, litmus paper, and chemical scanners that sense carbon monoxide and the percentage of oxygen in the atmosphere.

The hydrogen chloride produced by the burning solid fuel combines with water vapor from the fire and produces hydrochloric acid, Brown said.

Lt. Col. Bruce Rianda, Hill's deputy commander, said he expects the high temperatures generated during the fuel's burning will have destroyed the interior of the munitions igloo.

The domelike igloo, 65 feet long and 24 feet wide, is a concrete, earth-covered structure with double doors at one end.

Rianda said the igloo functioned properly when the propellant ignited. The flames and exhaust pressure blew the doors open, then struck an earthen berm, which directed it upward and away from other nearby igloos.

The 40,000 pounds of propellant is the amount carried in a Minuteman I missile's third stage, Rianda said. "You basically had a rocket out there," he said Tuesday.

Neal Faus, the chief of weapons safety for the Ogden Air Logistics Center at Hill, said the solid fuel rocket propellant was broken into chunks and placed in the bunker in 1963. There was no missile or missile motor in the igloo, only fuel, he said.

The fuel's deterioration over the years was being measured as part of what Faus called an "aging and surveillance situation." Minuteman I missiles are still part of the nation's defense arsenal, sitting in missile silos, and the Department of Defense wants to know if the fuel deteriorates over time, Faus said.

The fuel, in chunks ranging from fist-sized pieces to 100-pound blocks, is analyzed at least once a year to determine any changes in its potency or composition, Faus said.

Faus, along with Rianda and Murray, said no cause for Monday's fire will probably be determined for a month. No one was in or near the igloo when the fuel ignited, although a civil engineering crew was in the area and noticed the fire, Rianda said.

No injuries were reported in the incident, which also caused a small grass fire outside the igloo, Rianda said.

Rianda estimated the fuel burned in about five minutes, if all 40,000 pounds ignited, and the cloud of gas and smoke dissipated in about 10 minutes.

A security cordon, thrown up for 2,000 feet around the igloo and in effect Tuesday afternoon, required closure of the base's Roy gate, just off I-15, which also serves the base's museum.