PITTSBURGH (AP) _ Reports that toxic chemicals may have been dumped into the Ohio River while the water was fouled with diesel fuel have been turned over to Environmental Protection Agency criminal investigators, an EPA official said Wednesday.

Robert Boodey, head of the EPA Region III criminal unit in Philadelphia, declined, however, to say whether his office has opened a formal investigation. He said agency policy forbids commenting on criminal investigations.

''All I can tell you is we passed the information along,'' said Thomas Voltaggio, Superfund chief for Region III. ''Once we send the reports over to them we are really out of it. We want to separate any criminal activity from regulatory activity.''

EPA officials received the toxic dumping reports in mid-January, several weeks after the Jan. 2 collapse of an Ashland Oil Inc. tank near Pittsburgh fouled the Monongahela and Ohio rivers with an estimated 730,000 gallons of diesel fuel.

Sen. Arlen Specter, R-Pa., on Tuesday asked EPA to investigate the reports.

Traces of chloroform and methylene chloride, which both cause cancer, and another industrial solvent, 1,1,1-trichloroethane, were found in water samples by the West Virginia Department of Natural Resources, according to officials in that department.

They found no hard evidence, however, that the toxins were deliberately dumped to take advantage of the Ashland pollution crisis, said Ron Sandy, branch head of field opertions for the natural resources department.

The Pittsburgh Press reported Sunday that the toxic chemicals were found in a 15-mile stretch of the river between Wheeling and Moundsville.

The concentrations exceeded the levels set by EPA as cancer risks, but probably had no effect on public health, said Peter Tennant, water quality program manager for the Ohio River Valley Sanitation Commission.

''The intakes of all the water companies were shut down as the spill passed,'' Tennant said. ''Also, those compounds ... are easily removed by the carbon filtration systems water companies use.''

The tank collapse cut tap water service to about 23,000 suburban Pittsburgh residents and threatened to do the same for an estimated 1 million others. Water companies along the Ohio, which is formed by the Monongahela and Allegheny in Pittsburgh, closed their intakes and relied on reserves and emergency supplies until the diesel fuel passed.

The Pennsylvania Emergency Management Agency has helped process 70 claims against Ashland from municipal governments seeking a total of about $1 million, Karen Critchfield, PEMA disaster assistance officer, said Tuesday at a meeting of federal, state and local officials involved in the spill.