The cause is unknown, but this afternoon a DC Metro train and tunnel filled with smoke, causing injury to passengers and a slow evacuation of the L'Enfant station.

Washington Post:

Six people were injured, one critically, when smoke filled a Metro tunnel Monday afternoon.

Tim Wilson, a spokesman for D.C. Fire and EMS, said one person has been transported to an area hospital with a critical injury but he did not know the cause or severity of the injury. Another five people were transported with minor injuries.

The one person mentioned there has died, and another remains in critical condition along with another 60-65 who were taken to local hospitals for evaluation or less critical injuries.

Rider Jonathan Rogers' tale is pretty harrowing:

“You could see smoke coming through the doors,” he said. “It started to get scary pretty quick.”

He said the train operator got on the loudspeaker and urged people to remain calm. He said the plan was to back up the train to the platform of the L’Enfant station.

[...]

“People started praying,” he said. “Smoke was coming in pretty steadily. Some people were fine and some people were just hurting pretty quickly.”

He said a man standing next to him, started having breathing problems and sank to the floor.

Passengers watched out for each other, sharing inhalers with those who were having trouble breathing, he said. After a few more minutes, another woman standing near him said she couldn’t breathe and then passed out. Rogers and other passengers took turns giving her CPR.

“We just kept doing (CPR), maybe 25 minutes . . . we just kept going. Somebody helped carry her toward the back of the train – that was before the fire fighters arrived.”

Rogers said it took about 40 minutes before firefighters arrived and began evacuating the train. Passengers walked through the tunnel back to L’Enfant station. He said the air in the tunnel was easier to breathe than the air on the train. On the train, he said the smoked had a chemical smell, but in the tunnel it had the distinct smell of burning wood. Once they got to L’Enfant he saw a lot of ambulances and fire trucks.

[Photo Credit: Lesley J. Lopez on Twitter]