Sen. Barbara A. Mikulski (D-Md.) speaks Wednesday about the recent Metro smoke incident. Appearing with her were Sen. Mark Warner (D-Va.) left, Sen. Benjamin Cardin (D-Md.) and Del. Eleanor Holmes Norton (D-D.C.). (Cliff Owen/AP)

A breakdown in radio communications and problems with ventilation in the subway tunnel and train involved in last week’s fatal Metro incident aggravated a crisis in which scores of passengers were stuck in smoke-filled rail cars for more than 30 minutes, members of Congress said Wednesday night.

After being briefed behind closed doors by the acting chairman of the National Transportation Safety Board, members of the Washington-area congressional delegation emerged from the meeting to publicly share a few new details about the Jan. 12 incident, in which one passenger died and scores of others were sickened by smoke.

“Stepping onto a train car shouldn’t require a leap of faith about your safety,” said Rep. John Delaney (D-Md.). “What happened on the Yellow Line earlier this month was completely unacceptable, and we cannot lose sight of that.”

As for ventilation problems, Sen. Barbara A. Mikulski (D-Md.) and Rep. Don Beyer (D-Va.) said the group was told that after the six-car train encountered smoke in the tunnel and abruptly stopped just south of the L’Enfant Plaza station, the train’s air-intake system was not turned off, meaning it drew smoke into the cars.

At the time, riders were gasping for air. One of them, Carol I. Glover, 61, of Alexandria, died of smoke inhalation, according to an autopsy.

The National Transportation Safety Board said last week that the smoke in the Metro tunnel near L'Enfant Plaza was caused by electrical “arcing,” which occurs when electricity escapes its prescribed path. Here's how that happens. (Jason Aldag/The Washington Post)

“We know the ventilation system sucked smoke into the train,” Beyer told reporters after he and other lawmakers were briefed by the NTSB’s Christopher Hart. But Hart, also addressing the news media, contradicted Beyer and Mikulski, saying investigators have not determined whether the air-intake system drew smoke into the cars.

“We are doing further investigation,” he said. “That is one of the things we’re looking at. Was it bringing smoke in? We don’t know that yet.”

Transit experts interviewed last week by The Washington Post also voiced concerns about whether tunnel fans near the L’Enfant Plaza station worked properly during the incident, and one Metro official told The Post that the agency’s maintenance records on the fans are not current.

Depending on the situation, Metro configures a series of large tunnel fans in various ways to remove smoke from tunnels in the proper direction. Hart said investigators are still looking into how the tunnel fans functioned on the afternoon of the fatal incident.

“We have tested the ventilation system and noted some anomalies,” Hart said. “I don’t have details as to what that anomaly is.”

During a D.C. Council hearing Tuesday on the incident, the outgoing Metro board chairman, Tom Downs, appeared to criticize an article in Sunday’s Post.

“The [insinuation] that the fans weren’t working was dead wrong,” he said. “The fans don’t need fixing, and that’s after the NTSB verified the status of the fans themselves. That’s the kind of thing that we can’t have, before you jump to a conclusion. That is actually part of the problem. That’s as far as I can go.”

Smoke and fire incidents on Metrorail since 2012
While still sporadic, smoke incidents have decreased since peaking at 20 incidents in June 2012. Fire incidents have remained fairly steady, peaking at 13 incidents in May 2014.

(Denise Lu/The Washington Post/WMATA)

After the Capitol Hill briefing Wednesday, Mikulski said: “The 13 of us in the room were all trying to get answers about what happened that horrific day. We left the meeting with lots of answers.”

But many of the lawmakers said numerous questions remained unanswered, including whether there are broader communication problems in the subway system, why it took so long for first responders to reach victims, and why the train in the tunnel was unable to be moved.

Lawmakers said D.C. firefighters and Metro personnel were using radios that day that had different encryption codes. Both agencies change the codes periodically.

The fire department apparently had changed its code, but for some reason the two systems had not yet been synced.

The fatal incident Jan. 12 occurred in a tunnel just south of L’Enfant Plaza station. About 3:15 p.m. that day, officials have said, a six-car Yellow Line train, which had just left the station, abruptly stopped after encountering heavy smoke.

While the passengers waited at least 35 minutes for help to arrive, smoke filled the cars, causing scores of riders to choke and become sick.

Before Hart agreed to brief the congressional delegation, there had been a clamor for more information about the incident — from Capitol Hill, from D.C. Mayor Muriel E. Bowser (D), from the D.C. Council and from the news media.

Investigators have said the smoke was generated by an electrical malfunction 1,100 feet in front of the train involving cables that carried high-voltage power to the third rail.

In an occurrence called “electrical arcing,” power escaped from those cables, causing heat, melting and smoke, according to the NTSB, which on Friday issued a short, sparsely detailed preliminary report of its investigation.

“I think we got some answers, but I think a lot of questions remain,” Sen. Mark R. Warner (D-Va.) said after the briefing.

Among the unanswered questions is whether the arcing occurred because the cables had deteriorated as a result of not being properly maintained by Metro.

“We know there was arcing,” Hart said Wednesday. “We don’t know why there was arcing.” Hart said NTSB would look to determine whether it was caused by aging equipment that needed repair.

Questions also remain about technical problems involving communications equipment used by first responders in the tunnel and about Metro’s initial call to the D.C. fire department to report the smoke. Metro reported “heavy smoke at our L’Enfant Plaza Metrorail station” but did not initially convey that passengers were aboard a train stuck in the tunnel, according to a transcript of the 911 call.

Earlier Wednesday, Bowser responded to comments by Downs, who told the D.C. Council that some publicly disseminated information about the incident — including the timeline of events — “is not accurate as it stands right now.”

Bowser said: “We’re committed to a top-down review. We’ve released the first phase, and we’ll release the [next] phase later in the week.”

Unlike Metro, which has declined to comment on specifics of what went wrong in the tunnel, Bowser’s office on Saturday issued a preliminary report on the incident.

The report said D.C. firefighters in the tunnel could not clearly communicate by radio with commanders aboveground because signal-boosting equipment was not working properly. The equipment is maintained by Metro, and fire officials had alerted the transit agency to the problem in a Jan. 8 e-mail, four days before the emergency, the report said.

Why Metro officials apparently did not act on the e-mail warning is unclear. As a result, with radio transmissions failing, firefighters in the tunnel had to resort to using cellphones and a system of personally relaying information to the outside.

At the council hearing Tuesday, members grilled Downs on several issues related to the crisis, including the reported communications problems, Metro’s protocols for cooperating with first responders during such situations and whether train passengers can self-evacuate during emergencies.

Downs offered few answers, instead echoing what Metro officials have been saying since the calamity occurred 10 days ago: that because the incident is under investigation by the NTSB, federal regulations bar the transit agency from commenting publicly.

The Jan. 8 warning to Metro — which came after firefighters did a routine check of tunnel radio equipment — was not the first time in recent months that the transit agency had been alerted to communications problems in the subway.

In an Oct. 20 letter to Metro, the Metropolitan Washington Council of Governments (COG) said there appeared to be a drop-off in the ability to make 911 calls in underground stations, on platforms and aboard trains in tunnels.

The letter, sent by a COG committee that monitors 911 operations regionally, said the committee “was made aware of the possible degradation of cell phone/smart phone access by Metro patrons” at underground sites. The letter said COG was “understandably concerned if there is a degradation of 9-1-1 access in Metro Rail and would appreciate being provided a current status report” about 911 access.

COG offered to do a systemwide test for Metro on whether 911 calls could be made from the subway using four service providers — AT&T, Sprint, T-Mobile and Verizon.

Although Metro promptly replied, saying the agency would like to take up the testing offer, COG spokeswoman Jeanne Saddler said, the transit agency has yet to make arrangements for such testing.

Ashley Halsey III, Mary Pat Flaherty and Aaron C. Davis contributed to this report.