CONOWINGO, Md. (AP) _ A Conrail freight train derailed late Monday and caustic soda leaking from a car that plunged into the Susquehanna River halted municipal water pumping, officials said.

No one was reported injured in the accident, in which about 20 cars of the 72-car train derailed.

Steve Lubetkin, a Conrail spokesman, said the caustic soda probably came from an empty tanker car that had previously been carrying the chemical. The empty cars usual contain residual amounts of materials they were carrying, he said.

''We're not talking thousands of gallons,'' Lubetkin said.

Ccaustic soda, or sodium hydroxide, causes burns to the skin and eyes, Dixon said.

Two cars ended up in the river and six along the edge, officials at the scene said. Two on the river bank contained chlorine, but neither appeared to be leaking, said Mike Dixon, spokesman for the Cecil County Emergency Management Agency.

No evacuations were ordered in the rural area of northeastern Maryland. ''There is no immediate threat to life or health of area residents,'' Dixon said. ''As a precaution, municipal water intakes south of the leak were shut down.''

Water pumping stations at Perryville, Havre de Grace and Deer Creek were ordered to stop pumping water from the river, said Bob Thomas, spokesman for the Maryland State Fire Marshal's office.

The stations send water to Baltimore, Perryville, Havre de Grace and several surrounding communities.

The train had originated in Harrisburg, Pa., and was on its way to Baltimore, he said.