One passenger died after smoke filled the L'Enfant Plaza metro station Monday afternoon, the Washington Metropolitan Area Transit Authority said. A total of 84 people were taken to hospitals.
The National Transportation and Safety Board released a statement saying "an electrical arcing event" sparked the incident.
"There was an electrical arcing event involving the trackside power cables (the third rail)," said a statement from the NTSB's Peter Knudson.
A six-car Yellow line train was southbound from L'Enfant station when sparks were noticed about 1,100 feet in front of the train as the tunnel filed with smoke.
"Passengers on the train self-evacuated.," Knudson said. "The train did not derail. There was no fire on the train."
The smoke was thick enough to prompt WMATA to suspend service on several lines, including parts of the Green and Yellow line, which both stop there. Blue, Orange and Silver lines were bypassing the stop for a period of time, but resumed service Monday evening.
Tuesday morning service will be dicey, according to the WMATA website
. "All Yellow Line service will be replaced with additional Blue Line trains" until the Yellow line returns to regular service. Other trains will be delayed.
Following the incident, emergency vehicles crowded the streets around the complex of office buildings that make up L'Enfant Plaza.
The buildings largely house private businesses, but the U.S. Postal Service is also headquartered at L'Enfant Plaza.
Alec Dubois, a freshman at Gonzaga College High School, told CNN affiliate WJLA he was in a tunnel on a train near the station when smoke started filling the air.
"People were freaking out, going everywhere. The conductor was telling us to stay calm. He said he was trying to get our train back to the station. We had no cell service. I was trying to call my parents. And then there was black stuff everywhere, it was all over my pants, too. It was under our noses. We have no idea what it was."
"We decided to go out one of the side doors and then we started walking on the rails," he said. "Once we got out of the station, we just sprinted for our lives...because we had no idea what was happening."
He described the smoke as "translucent."
Lesley Lopez, a metro rider who was there when the smoke broke out, said she "wasn't sure what was happening, and then I heard a voice say, 'Get out of the train station.'"
The longtime metro rider said, however, the evacuation was "poorly managed," and that she was "disturbed" by the fact she was given no evacuation instructions or indication of what had happened.
"It's disheartening because there did not appear to be an emergency plan," she said.
D.C. Mayor Muriel Bowser issued a statement following the incident thanking city first responders and offering her condolences to the family of the dead passenger.
Video from CNN affiliate WJLA showed emergency crews taking several people from the station on gurneys.