ABERDEEN PROVING GROUND, Md. (AP) _ A federal grand jury is investigating Army and civilian officials who oversaw the operation of a deteriorated testing center where highly hazardous substances were mishandled, The Baltimore Sun reported Sunday.

The investigation centers on alleged violations of federal environmental and worker-safety laws involving handling, storage and disposal of dangerous substances at the now-closed ''pilot plant'' at the Aberdeen Proving Ground, the newspaper said.

The substances included components of lethal nerve agents, sources told the newspaper.

Scores of Army documents were subpoenaed by the grand jury May 6 and delivered May 19. Some of the records allegedly had been falsified and supervisors had lied in an attempt to cover up some questionable practices at the plant, sources told the newspaper.

The investigation also has uncovered evidence that the Army appeared to have used the plant for storing hazardous waste from bases around the country, as well as from the Proving Ground, the sources said.

John A. Yaiquaint, a spokesman for base commander Maj. Gen. Charles F. Drenz, referred all questions about the investigation to Breckinridge L. Willcox, U.S. attorney for Maryland.

Willcox on Saturday would neither confirm nor deny the investigation.

Sources told the newspaper that the grand jury asked for records dating back to January 1982 from the base headquarters and from the Army's Chemical Research, Engineering and Development Center, know as CRDEC, which operated the pilot plant.

Before it closed in February 1986, the plant performed preproduction studies on the Army's binary chemical weapons systems, scheduled to go into production later this year.

The dilapidated, 46-year-old pilot plant building is located at the base's Edgewood Arsenal, near the upper end of Canal Creek, a tidal stream that flows into the Gunpowder River, which flows into the Chesapeake Bay.

The newspaper last year reported problems at the plant, including the alleged illegal burning and dumping of chemicals and unsafe exposure to workers.

In March, the Army acknowledged the problems and said the plant would be closed except in the case of emergency.