A "loud explosion-type sound" rocked a computer operations center at the Washington Navy yard early today, minutes after military officials were warned that a bomb would go off there at midnight, authorities said.

Lt. Cmdr. Bill McLoughlin said this morning that he could not confirm any damage to the building, which houses the Navy Regional Data Automation Center. No injuries were reported.

The explosive noise apparently came from the fourth-floor of that building, McLoughlin said.

An apparently recorded warning was telephoned to the Navy district duty officer at 11:56 p.m. that a bomb would go off in the Department of Defense Computer Institute, McLoughlin said. A training facility, the institute is in the building next to the automation center, McLoughlin said.

The automation center is a regional center for several military commands in the Washington area, he said.

"We had at least 15 confirmed reports from personnel working in the yard that either stuff came off the wall, bulletin boards, coffee cups falling on the floor," said James Shepherd, assistant chief for the fire department for the Naval District of Washington.

He said about at least one person, a security guard, was in the building at the time the noise was heard.

Shortly after the blast-sound was heard, The Washington Post and United Press International received apparently recorded messages by phone, claiming that the FALN, a Puerto Rican nationalist group, was responsible.

An unidentified male caller told The Post in a call at about 12:15 a.m. said that the "attack" on the Navy Yard was to "strike a blow against the imperialist. . .United States war machine" in Nicaragua.