Since the tragedy, D.C. Mayor Muriel Bowser has struck a cautious tone, refusing to draw conclusions or to blame Metro, where she previously served as a board member. (Linda Davidson/The Washington Post)

The District government contradicted Metro on Friday in an escalating dispute over the failure of emergency radios as passengers sat waiting for help this month in a smoke-filled train trapped in downtown Washington.

The city’s homeland security agency issued a report partly disagreeing with an explanation offered just a day earlier by Metro that implicated the city fire department in the communications breakdown in the Metro tunnel. According to the report, fire officials had told Metro about the radio trouble, and Metro had not fixed it.

Firefighters resorted to cellphones and a chain of runners to relay information during the Jan. 12 incident, which killed one passenger and hospitalized more than 80 others. Neither Metro nor the administration of new D.C. Mayor Muriel E. Bowser (D) have alleged that working radios would have saved 61-year-old Carol I. Glover, the Alexandria woman who died of smoke inhalation as passengers waited over 35 minutes for rescues.

But the dispute over radios has exposed what firefighters say has been a tense relationship for years between Metro and the city’s first responders, and it has raised questions about the ability of the two agencies to work together effectively in emergencies.

Metro spokesman Dan Stessel declined to comment on the report, saying the National Transportation Safety Board “is the only impartial agency conducting a fact-based investigation into this matter.” Stessel said Metro continues to give its “full cooperation” to the federal investigation.

The National Transportation Safety Board said Tuesday 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)

The District’s report, however, partly disputed the account offered Thursday by Metro’s interim general manager, Jack Requa, and his deputy, Rob Troup, regarding the meltdown near the L’Enfant Plaza station, which resulted in the transit system’s first fatality involving a train rider in six years.

Requa said Metro radio technicians had discovered in the days since Jan. 12 that the fire department had previously changed the way its radio signals operate but had not informed Metro of the change. Those changes included new encryption and an increase in the number of channels, Troup said.

Metro’s subway system is equipped with signal-relaying equipment that should allow firefighters to use their radios below ground. The radios did not function properly during the rescue, Requa said, because Metro had not altered its relaying equipment to conform to the changes made by the fire department.

The report released late Friday by the District’s Homeland Security and Emergency Management Agency, or HSEMA, offered a different account.

It said that D.C. Fire and Emergency Medical Services officers had worked closely with Metro to make sure that new digital radios allow encrypted signals to work consistently in tunnels. The report said more than 600 tests had been done in the past two years as the radios were put into use. Radios had worked as recently as a series of tests conducted in three stations Dec. 8, the report said.

However, when responding to a call for a debris fire Jan. 7, firefighters found that their radios were not working at the L’Enfant Plaza station. “WMATA was notified of the issue, but repairs were not made prior to the January 12 incident,” the report said, echoing a similar finding last week in a report by D.C. firefighters.

The report concluded that there is no evidence that radio encryption affected the performance of the radios.

“Based on the currently available information, the FEMS radio encryption function does not appear to have played a role in the communications difficulties experienced by FEMS personnel inside the L’Enfant Plaza Metro Station and tunnel,” the report said.

The city’s explanation, focusing on radio encryption, was more narrowly drawn than Metro’s. On Thursday, in an interview after a public board meeting, Metro Deputy General Manager Rob Troup said: “We don’t know if the radio problems were totally tied to encryption. When we got to see what had been changed, there were other things there. They’d added channels, seven channels as I recall, so that was another thing we saw.”

The D.C. homeland security agency’s report also said encryption is not an ongoing problem. The report corroborated statements made Thursday by Metro’s Requa that emergency radios are again working in the tunnels. Since Jan. 12, according to the report, systemwide testing of firefighters’ radios had been conducted in every Metro station and in tunnels to assess signal strength and audio quality.

The report offered a few new tidbits of information — for instance, that the operator of a second train, stopped behind the stalled train, had evacuated with the passengers. The position of that train may have prevented the train stuck in the smoke from backing up to the station to let passengers out. The report for the first time also referred to the electrical arcing involving the electrified third rail as a “fire.” Previously, Metro had called it a “smoke incident.”

District homeland security officials did not have access to more than 370 hours of surveillance video, which Metro said it has turned over to the NTSB. Stessel said the transit agency has also delivered more than 4,000 pages of documents to federal investigators.

Christopher Geldart, the homeland security director and a holdover from the administration of former Mayor Vincent C. Gray (D), was in charge of the report. But it was Bowser, city officials said, who gave the final approval to the report Friday night. Officials did not immediately respond to a question about whether Bowser had sought edits to the report.

Since the tragedy, Bowser has struck a cautious tone, refusing to draw conclusions or to blame Metro, where she previously served as a board member. Beyond pushing back on the radio issue in technical sections of the report, the release again showed Bowser’s measured approach.

In a two-paragraph section labeled “Conclusions and Next Steps,” the report stated that more “after-action review” is planned. Its conclusion:

“It is important to consider the potential for larger, more complicated incidents to occur in the future, where agency roles and responsibilities may be stressed in more challenging ways. The District should be proud of the response that its employees and citizens delivered on January 12, but it should also recognize the need for an ongoing commitment to continually build and test capabilities through training, exercise, and real-world event responses.”

Lori Aratani, Paul Duggan and Mary Pat Flaherty contributed to this report.