Update as of 11:30 p.m. EST: "An arcing event" involving the third rail and cables that supply power was detected, WTOP reported, citing an official with the National Transportation Safety Board (NTSB).

A tunnel filled with smoke, forcing the evacuation of a Washington Metro station, leaving one person dead and sending 84 people to the hospital, the Washington Post reported. The cause of the smoke was not immediately determined.

Passengers were rescued from a train from the tunnel at L’Enfant Plaza. The incident began at 3 p.m Monday. Some subway lines were suspended and others bypassed the station.

The injured were taken to George Washington Hospital, Howard University Hospital and Washington Hospital Center, the Post reported. More than 200 people were evaluated after the incident, the LA Times said.

Smoke filled the train as the driver tried to back up, the Post said. One rider said passengers tried to help each other, and a few took turns giving a fellow passenger CPR when she passed out, the Post reported.

Some riders on a nearby train also saw the smoke and decided to leave through the side doors, CNN reported. They began to walk on the rails until they were able to escape the station near the National Mall and the Smithsonian National Air and Space Museum. As of 8:13 p.m., L’Enfant Plaza Metro station had reopened.

Many flocked to social media to post photos and statuses about the experience.

The name of the woman who died has yet to be released.

The National Transportation Safety Board opened an investigation.

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