TUCSON, Ariz. (AP) -- Tucson environmental officials want to find out how far fuel leaks have spread into the ground water supply near the city's convention center.

Test wells will be going up this week in the downtown area to check water samples.

The source of the contamination comes from old gasoline storage tanks used in the 1980's by the Tucson Police and Fire Departments, city officials said.

The Police and Fire departments and other city departments filled their vehicles at a fueling station between the Police and Fire departments' headquarters from the late 1970s until the tanks were removed in 1993.

Environmental officials have determined the leaking underground storage tanks did not pollute drinking water, a city official said.

Test wells set up earlier found dissolved and floating benzene in groundwater 65 feet below the street. The drinking water supply is 130 to 140 feet down, said Richard Byrd, a senior hydrologist in the city Environmental Services Department.

Benzene is found in gasoline and is a known human carcinogen, according to the U.S. Environmental Protection Agency.

"There's no immediate risk to the public or health risk at this site," said Steve Owens, director of the Arizona Department of Environmental Quality.

State law does require all groundwater to be treated the same, whether it's drinking water or not.

"All ground water is potential drinking water," Owens said. "It's very important where we are aware of groundwater contamination, that if we have the resources to clean it up, we clean it up."

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Information from: Tucson Citizen, http://www.tucsoncitizen.com

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