Smoke filled the L’Enfant Plaza Metro station in Washington, D.C., on Monday, killing one woman and sending dozens of people to the hospital. The cause of the smoke wasn’t immediately clear, but authorities evacuated the busy subway station and temporarily shut down service on several lines. A total of 83 people were injured due to the smoke, including two who are in critical condition, according to D.C. Fire Department spokesman Tim Wilson. The National Transportation Safety Board was investigating the incident and told reporters at a briefing that “an electrical arcing event” happened about 1,100 feet in front of the train and filled the tunnel the smoke. Arcing involves cables that power the third rail and can generate smoke through connections with short circuits. There did not appear to be a fire but the cause of the smoke has yet to be determined, Metro General Manager Richard Sarles said.