The evacuation of the 1st Police District headquarters early Thursday was caused by a chronic gasoline spill that left at least 16,000 gallons of gasoline and water, contaminating the soil and possibly the ground water under the building, city officials said yesterday.

The D.C. Department of Health is investigating the possibility that two underground storage tanks at the station house had been overfilled with gasoline over a 17-year period, said Theodore J. Gordon, deputy director of health for environmental health. Over time, the gasoline may have gradually seeped into the soil, he said.

After last week's heavy rains from Hurricane Floyd, the gasoline was forced out of the soil and into the basement of the station house in the 400 block of Fourth Street SW.

The fumes presented a serious hazard because the basement's pump was broken, Gordon said. The area flooded, causing gasoline fumes to build up, he said. "If there was a spark in the basement, or if someone was smoking, it may have caused the building to explode," he said.

The Health Department is asking the Department of Public Works to provide documentation identifying the government contractors who delivered the gasoline, Gordon said.

The tanks have not been in use since a 1998 mandate by the U.S. Environmental Protection Agency required all places with underground gasoline tanks to either close or upgrade them. By then, the overflow was already in the soil, Gordon said.

So far, a total of 16,000 gallons of combined water and gasoline have been removed. About 400 tons of contaminated soil also were taken out, and the two gasoline tanks were taken to a disposal site. "We are going to keep the area closed until the soil is taken out. The vapors are still there in the soil," he said.

Officers were evacuated from the station house early Thursday after three police officers became sick from the fumes. All three were treated and sent home.

The problem has not disrupted operations, said Cmdr. Kim C. Dine. Some operations are now at the 1st District substation at Fifth and E streets SE. Other officers are working out of Chinatown. Dine said he hoped to have officers back in the building by tomorrow.