Federal and state environmental officials are becoming concerned that scores of abandoned coal mines in Pennsylvania have become illegal dumps for dangerous chemical wastes trucked in from throughout the Northeast.

The officials became alarmed recently when a drainage tunnel connecting three miles of abandoned mines in northeastern Pennsylvania near Pittston began leaking thousands of gallons of cancer-causing chemicals into the Susquehanna River.

The Pennsylvania department of environmental resources estimated that the leaking mines may contain between 300,000 and 500,000 gallons of oil and chemical waste dumped there.

Pennsylvania officials said yesterday that the amount of chemical waste gushing from the Butlet Tunnel into the river had diminished from several thousand gallons daily to several hundred gallons.

But they said that after the spill was discovered two weeks ago investigators found traces of dichlorobenzene, a suspected carcinogen, in the outflow and in the drinking water supply of Danville, Pa., some 60 miles downstream from the leak.

Officials said yesterday that the water was safe to drink but they added that they are testing fish caught in the river because some of the carcinogens leaking from the mine tunnel tend to accumulate in fish over time.

Swimmers were also told by the state not to use the river because contact with the leaking chemicals could cause rashes and nausea.

Pennsylvania officials became so concerned about the leaking chemicals that they made operators of a dam at Shamokin, Pa., lower the water level last week so the overflow from the dam would not churn up the Susquehanna and push the chemical waste toward other water systems.

James Chester, regional director for the state's environmental resources department, said yesterday that his investigators are running tests on three more mine drainage tunnels near Wilkes Barre, Pa., where chemicals apparently also have been dumped.

"We are finding large and repeated evidence that these mines are being illegally used by dumpers," he said.

Investigators in Pennsylvania have identified trucks bound for the mines from Ohio, New Jersey, Connecticut, New York and other northeastern states, he said.

One truck filled with chemical waste and bound for the mines was recently sent back by the state to Rockefeller University in New York City, said Chester.

Officials said that pressure to find legal dump sites for hazardous waste has increased recently, forcing waste producers to either pay huge disposal fees to legitimate firms or look the other way and get rid of dangerous material with illegal dumpers.

Pennsylvania officials recently said one coal company had allowed such firms to dump 4,560 drums and 29 truckloads of hazardous waste in abandoned mines in southwestern Pennsylvania near the Maryland border.

When officials locate an illegal dump site, they said, they often can't identify who owns the mine. In the case of coal shafts, Chester said his investigators have found the mines often are long-forgotten properties belonging to a family estate.

"We tried to locate the owner of the mines draining into the Butler Tunnel," he said. "The last deed of sale we could find was dated 1864."