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Pablo Martinez Monsivais, Associated Press
National Transportation Safety Board (NTSB) Acting Chairman Christopher A. Hart, center, with NTSB members Robert L. Sumwalt, left, and Earl F. Weener, right, answers questions regarding yesterday's subway incident during a NTSB news conference in Washington, Tuesday, Jan. 13, 2015. The transit network in the nation's capital, which is being investigated the incident, remains hobbled after an electrical malfunction that filled a busy subway station with smoke, killing one woman and sending dozens of people to hospitals.

WASHINGTON — The transit network in the nation's capital was hobbled Tuesday after an electrical malfunction filled a busy subway station with smoke a day earlier, killing one woman and sending dozens of people to hospitals.

Smoke started filling the train and station at the beginning of the Monday afternoon rush hour and led to the first fatality on Washington's Metro system since a 2009 crash killed eight passengers and a train operator.

National Transportation Safety Board investigator Michael Flanigon said the smoke started when something came into contact with the high-voltage third rail, which powers the train. He called it an electrical "arcing" event. There was no fire, and what caused the smoke was not yet known.

Witnesses described a chaotic scene aboard the train as passengers tried to escape the smoke, and many left the train on their own before emergency responders arrived, Flanigon said. In addition to a woman who died, at least one other passenger was in critical condition at a local hospital. Eighty-four people were taken to hospitals, most with smoke inhalation, authorities said.

Passenger Jonathan Rogers, 31, who works for the District of Columbia Department of Transportation, said he and two other people tried in vain for 20 minutes to revive a middle-aged woman who had slumped to the floor unconscious as their car near the front of the train quickly filled with smoke.

"We know you do chest compressions and mouth-to-mouth, so that's what we did," Rogers said in an interview Tuesday morning. "Nothing was happening and she was laying there unconscious. Somebody took her pulse and said they couldn't feel a pulse."

Rogers said a man scooped the woman up in his arms and carried her through the cars toward the back of the train.

It wasn't immediately clear if the woman was the same woman who authorities said died on the train.

Rogers said he doesn't understand why passengers weren't allowed to leave the train sooner for the one- or two-minute walk back to the platform.

"It just kind of felt like, 'Why were we trapped on that train that long?'" Rogers said. "All we did was sit there and wait. Forty minutes seems like a long time."

The smoke started around 3:30 p.m. Monday on a Virginia-bound yellow line train that had just left the L'Enfant Plaza station in downtown Washington, one of the system's busiest stations. The train stopped about 800 feet beyond the platform, and the arcing occurred roughly 1,000 feet beyond the train, Flanigon said. The train did not derail, he said.

The Metrorail system, which connects downtown Washington with the Maryland and Virginia suburbs, carries an average of 721,000 passengers each weekday. The system's yellow line remained shut down Tuesday morning, and the system's orange, blue and silver lines were on a reduced schedule. Service on the green and red lines was normal.

Smoke and fire are not unusual on the aging subway system, which opened in 1976 and still uses some original rail cars. Metro's most recent quarterly safety report showed 86 incidents of smoke or fire in 2013 and 85 such incidents through the first eight months of 2014.

Metro riders on Tuesday expressed varying degrees of concern.

William Coates, 42, of Oxon Hill, Maryland, who was waiting to catch a train at the L'Enfant station, criticized Metro's response time. It "should have been a lot faster than it was," he said.

Devin Krotman, 28, who was getting off at the L'Enfant station, said he was concerned that Metro may not be practicing enough for emergencies.

"I don't think there's a lot of trust in how Metro handled this situation," said Krotman, a government contractor.

Associated Press reporter David Dishneau in Hagerstown, Maryland, contributed to this report.

Follow Ben Nuckols on Twitter at https://twitter.com/APBenNuckols .