A Metro train approaching the National Airport station derailed last night, disrupting subway service to two Virginia stations for several hours but causing no injuries.

"People were scared to death," said Charles Rogers, one of about 30 passengers aboard the Blue Line train. "But everybody was trying to be pretty cool. Nobody panicked."

The forward-most wheels of the lead car of the six-car train left the tracks about 50 feet short of the elevated passenger platform about 8:25 p.m., according to a Metro official.

Several passengers told a reporter they felt the slowly moving train lurch to a stop, and then the lights went off.

The train remained upright and its operator helped the passengers descend a short ladder and led them along the tracks to the station.

Metro officials said the derailment was caused by a switch malfunction and that maintenance crews had been working earlier yesterday on the track's electrical system. Metro spokesman Cody Pfanstiehl said the possibility of a connection between that repair work and the derailment was under investigation.

Pfanstiehl said full Metrorail service is expected to be restored before this morning's rush hour.

Switches at the National Airport station have been wearing out at an unexpectedly fast rate because of an unusual three-track configuration at the switching point, according to Metro officials.

Switching malfunctions are uncommon on the Metro system, and there have been few derailments. There has been at least one other derailment at the switching point near the National Airport station.

A switching malfunction triggered the worst accident in Metro's five years of operation last Jan. 13 when a New Carrollton train left the tracks between the Smithsonian and Federal Triangle stations and three passengers were killed.

Last night's derailment disrupted service at the National Airport and Crystal City stations. About 200 passengers were bused to the nearest operating Metro stations during the approximately three-hour disruption of service.

Many of the inconvenienced passengers were meeting friends on incoming planes at the airport or were returning to Washington from out-of-town trips.

"Welcome home," muttered Doreen McGirr, who was returning to Washington from Minneapolis, adding: "But we were lucky we were not on it the train ."

Steve Davis, 22, who works at a downtown office, said the derailment would add two hours to his commuting time from the city to Mount Vernon.