Subway service on the Blue and Orange lines was disrupted yesterday morning because of an electrical malfunction on a train near the Farragut West station. Metro officials said the incident caused delays of more than 30 minutes for thousands of rush-hour commuters.

Trains on the Blue and Orange lines were temporarily halted at other stations and in subway tunnels after electrical power was shut off between Foggy Bottom-GWU and McPherson Square to allow workers to repair the faulty equipment, a Metro spokesman said. No delay was reported on the Red or Yellow lines.

The Farragut West station was closed for about 30 minutes after the 8:38 a.m. incident as a precaution because of smoke and sparks caused by the malfunctioning electrical device, said Metro spokesman Allen Long.

Long said the malfunction was traced to a damaged electrical cable in a device known as a collector assembly, which carries power from the subway system's third rail to the train's motors. One end of the cable was found to be brushing against the tracks and the train's side, causing sparks and smoke.

Passengers on the disabled train, which was bound for New Carrollton, were allowed to get off at Farragut West, Long said. But several hundred riders were forced to wait on another train in a tunnel a short distance behind the disabled train until repair work was completed.

Because of the shutoff of electricity, Long said, the passengers were left without air conditioning.

No fire occurred, Long said, and no injuries were reported. Service on the interrupted section of the lines resumed at 9:26 a.m., he said.

Metro officials dispatched four buses to transport subway riders between Foggy Bottom-GWU and McPherson Square, but Long said they proved unneeded. "By the time the buses got there, the incident was over. They didn't carry anybody," he said.

Service was maintained with only minor delays on sections of the Blue and Orange lines east of McPherson Square, Long said. The principal delays, he said, occurred on parts of the lines linking Foggy Bottom-GWU with stations in Northern Virginia.