An electrical fire broke out yesterday morning in a malfunctioning Metro subway car that had been cleared of passengers moments earlier. No one was seriously injured, but train service was disrupted for about an hour, Metro officials said.

It was the first fire in the subway system since it began operations in March, 1976. The fire broke out as a supervisor and a train operator were taking an otherwise empty train to the main Metro yard for repairs.

The train had just left the tunnel under Union Station and was heading above ground in the direction of Rhode Island Avenue when the fire was discovered, according to Ralph Wood, Metro's chief of operations and maintenance.

Power was cut to the rails in both directions as firefighting equipment was brought in. Buses were used to shuttle rail passengers between the Rhode Island Avenue station and Union Station and Dupont Circle, the end of the line.

Damage was confined to electrical wiring under the floor of the car, although there was heavy smoke. "The fire never got into the seats or the passenger compartment," said D.C. Battalion Fire Chief Harry Shaffer.

The fire was extinguished and the train removed to a siding within an hour, officials said.

The train operator, Leeborn Goed, told officials he was not feeling well after the incident because of the heavy smoke, but he was not hospitalized.

"No fire is good," said Chief Shaffer, "but this did turn out to be quite a good learning experience for us." Metro and the Fire Department have been conducting safety and evacuation drills in preparation for the opening of 12 more subway miles in July.