A small explosive device caused minor damage to the outside of a building housing a computer operation at the Washington Navy Yard early yesterday, Navy authorities said.

A team of FBI agents and investigators from the D.C. Police and the Navy found "several articles believed to be used in an exploding device" outside the Navy Regional Data Automation Center building, Navy officials said in a prepared statement yesterday.

Navy and police officials declined to say what sort of bomb they believe was used at the Navy Yard facility in Southeast Washington.

There were no injuries in the explosion, which occurred at 12:04 a.m. yesterday. More than 20 Navy and civilian personnel, some inside the data automation center building, heard the explosion, said Navy Yard spokesman Lt. Aaron Long.

The explosion did about $1,000 damage to the southeast side of the building and the surrounding area, police said.

The explosion followed by eight minutes an apparently taped message telephoned to the Navy Yard warning that there would be an explosion at the Department of Defense's Computer Institute, a computer training facility there.

The institute is separated from the building where the bomb was detonated by a large parking lot two blocks long, Long said. The data automation center designs computer programs for various Navy operations, Long said.

The taped telephone message to the Navy Yard said that a group called the FMLM was responsible for the bombing, police said. The organization is a splinter group of the FALN, (Armed Forces for National Liberation) a Puerto Rican terrorist group, police said.

Shortly after the explosion, The Washington Post and United Press International each received an apparently taped message by telephone stating that the FALN was responsible.

Navy officials have "no idea" why either facility at the Navy Yard might be the object of a bombing, Long said.

The bombing follows by four months another small bombing at the entrance to the National War College building at Fort McNair in Southwest Washington. The April 16 bombing did only slight damage to the front of the building.