An electrical malfunction that filled a Washington subway train with smoke, killing one passenger and sickening dozens more, continued for 44 minutes before the Metro transit agency shut off power to the affected rail, federal investigators said Friday.

The malfunction began at 3:06 p.m. Monday in a tunnel near the L'Enfant Plaza station in downtown Washington, the National Transportation Safety Board said in a preliminary report.

The affected train, which was headed for Virginia, stopped in the tunnel at 3:15 p.m., about 1,100 feet short of the source of the smoke, the report said. One minute later, Metro began ventilating the tunnel in an effort to push out the smoke. But Metro didn't shut down power to the affected rail until 3:50 p.m., according to the report. The power was shut down remotely from the subway system's command center.

District of Columbia officials have said their emergency response was delayed because Metro didn't say whether the electrified third rail had been shut down between the platform and the train. The train operator repeatedly told passengers to stay put, and many remained on the train for at least a half-hour before firefighters began evacuating them. Some left the train on their own and walked back to the platform, ignoring the operator's instructions.

District officials said firefighters first reached the train at 3:48 p.m. — two minutes before power to the affected rail was cut off.

Some passengers are already suing Metro for negligence. One of those passengers, Malbert Rich, 53, said he composed final text messages to his mother and children while aboard the train, thinking he might not survive.

Carol Glover, 61, an information-technology analyst from Alexandria, Virginia, died of acute respiratory failure due to smoke exposure, according to the city medical examiner's office. Fellow passengers performed CPR on her before emergency medical workers arrived, and she wasn't taken to a hospital until more than an hour after the train began filling with smoke.

The accident was the first fatality on the nation's second-busiest subway system since a 2009 crash between two trains that killed eight passengers and a train operator. A Metro spokesman declined to comment Friday on the NTSB report.

A second train arrived at the station at 3:25 p.m., the report said, and its passengers were also exposed to smoke.

Passengers said the conductor told them repeatedly that he planned to back the train up and return it to the station once the other train cleared the platform, but aside from several lurches, the train didn't move much at all.

The report does not say what caused the malfunction, which caused severe damage to the third rail and electrical cables. The NTSB is reviewing records on maintenance and previous events with smoke, employee training records and Metro's emergency response and evacuation plans. Investigators are also interviewing the Metro employees involved and reviewing surveillance video.