ANCHORAGE, Alaska (AP) _ A fire in a chemical-filled warehouse sent a toxic plume into the air, forcing hundreds of workers from their sites at Prudhoe Bay, officials said.

There were no reports of injuries and the fire was contained three to four hours after it began at 5:20 p.m. Tuesday, said officials of Dowell Schlumberger Inc., owner of the warehouse near the oil-service camp of Deadhorse.

Brad Fristoe, the Alaska Department of Environmental Conservation's North Slope district manager, said the building essentially was left to burn because the nature of the fire made it difficult to fight.

Fire crews from the two major North Slope oil producing companies, ARCO Alaska and BP Exploration (Alaska), responded to the blaze, said Louis Steinke, a Dowell Schlumberger manager in Anchorage.

Houston-based Dowell Schlumberger maintains oil wells at Prudhoe Bay. There are at least two other companies that provide similar services, and the fire did not interrupt the flow of oil from Prudhoe Bay, which supplies 20 percent of the nation's crude.

Fristoe said at least 1,000 workers were evacuated.

Occupancy at the Prudhoe Bay Hotel, several miles from the fire, swelled to about 500 people, up from the usual 260, said Staci Bolley, acting manager.

''We are crammed,'' she said this morning. ''We are packed wall to wall. We have people sleeping on the floor.''

Fristoe said the DEC would investigate the possibility of a chemical spill on the tundra, the delicate arctic layer of plants that can take years to regenerate. Steinke said there was no evidence of a spill.

''The plume was caused by a number of the chemicals they had within the building,'' he said. The warehouse contents included lubricants, acid and solvent, he said.

Acid-containing tanks with capacities in the thousands of gallons were outside the warehouse and remained intact during the fire, Fristoe said.

He said he doesn't know when the area will be reopened.

''It all depends on what kind of materials we find and the situation there,'' he said. ''It could take days to open up that area completely.''