CLEVELAND (AP) _ BP Amoco plans to post signs warning customers not to use cellular telephones near gasoline pumps at its U.S. stations by year end, a company spokeswoman said today.

The precautionary measure is prompted by concerns that electronic impulses from a cellular phone could help ignite fires if gasoline or gas fumes are present. The risk is slight, but London-based BP Amoco doesn't want to take any chances,said Linda McCray, a BP spokeswoman in Cleveland.

The signs at the Amoco and BP stations will have a picture of a cell phone enclosed in a red circle with a slash through it, McCray said.

``This is not a ban _ this is a precautionary warning,'' McCray said. She said customers still will be allowed to use cell phones away from gas pumps.

Nancy Malinowski, a spokeswoman for the San Francisco-based Chevron Corp., told The Plain Dealer that Chevron will place warning decals on gas pumps later this year.

The city of Cicero, Ill., a Chicago suburb, recently passed the first law in the nation banning the use of cellular phones at gas stations.

Cell phone manufacturers have included warnings against such use in owner's manuals for years because they say that under certain conditions, cell phones could help generate sparks.

The American Petroleum Institute, which is looking into the reports, has so far found no substantiated reports of fires.