Three persons -- a Air Force enlisted man and an enlisted woman and one civilian -- were killed at Andrews Air Force base last night in an accident that occurred as they were trying to find the cause of a leak on the top floor of a dormitory.

A base spokesman said early today that the causes of the three deaths had not yet been determined. Initial reports, however, indicated that the three may have been electrocuted, possibly through contact with wires running near the roof of the three-story dormitory.

The names of the three victims were not immediately released, pending the notification of relatives.

Based on what he described as sketchy preliminary reports, the base spokesman, Lt. Col. Bob Thatcher, said the accident apparently occurred some time before 9:30 p.m. as the three victims were working with a ladder on the outside of the brick dormitory.

Thatcher said early this morning that no witnesses had yet been found who could tell exactly what happened to the three. All three were found unconscious on the ground outside the building, apoparently near the ladder.

Emergency personnel were summoned. The two men, the civilian contractor and the enlisted man were taken for treatment to the Malcolm Grow Air Force hospital, which is located at Andrews about three-quarters of a mile from the dormitory.

The woman was taken to Southern Maryland Hospital Center in Clinton, which is within a few miles of the base.

The civilian was pronounced dead at 10:42 p.m. and the enlisted man six minutes later. The woman died at Southern Maryland at 11:09 p.m.

The dormitory where the accident occurred houses a medical services unit attached to the base hospital. The two enlisted victims were attached to the unit, but were housed in other quarters, Thatcher said.