A track fire sent smoke pouring into a Metro tunnel, leading to chaos on a Red Line train that had to be evacuated and disrupting service for several hours. (Thomas Johnson/The Washington Post)

The Federal Transit Administration is investigating a track fire that sent smoke pouring into a Metro tunnel Saturday, leading to chaos on a Red Line train that had to be evacuated and disrupting service for several hours.

Passengers aboard the train described a tense atmosphere, with smoke in some of the railcars, flames visible outside the train and the odor of electrical smoke evoking memories of the Jan. 12, 2015, L’Enfant Plaza Metro station calamity that left one rider dead and scores sickened. No injuries were reported in Saturday’s incident.

The fire, which occurred near the Friendship Heights Metro station, prompted inspections of large portions of the Red Line and even some trains. Metro said tracks were inspected from Van Ness-UDC to Medical Center stations, and several trains passing through the area were flagged for inspection. Service was suspended between the Van Ness-UDC and Medical Center Metro stops while fire officials investigated.

Metro spokesman Richard Jordan said in an email that inspections “were conducted over a long stretch of the Red Line, not only on the outbound track (where the incident occurred), but also on the inbound track. Once a cause is known, we will be in a position to discuss mitigation.”

He declined to answer questions related to what was found during those inspections, citing the ongoing investigation.

A look inside the smoke and fire defects that paralyzed D.C. Metro

D.C. Council member Jack Evans (D-Ward 2), the chairman of the Metro Board, said worn equipment probably was to blame. Whether the fire might be related to water intrusion, long the culprit behind electrical issues on the Red Line or perhaps faulty cables, the cause of a one-day emergency systemwide shutdown last month, remained to be seen.

The incident, first reported at 7:18 p.m. Saturday, appeared to involve an insulator, and Metro said it was “possibly the result of electrical arcing.”

“My overriding observation is this: Whatever it is, the system is old and these fires are caused, not always but in large part, by things that are wearing out,” Evans said. “It goes back to the whole observation that the system needs a huge overhaul from top to bottom, and until that happens, I think these incidents are going to occur.”

The FTA assumed safety oversight of Metro’s rail operations in October, making it the first U.S. subway system to fall under such scrutiny. The agency said Sunday that it sent two of its Metro safety oversight inspectors to investigate Saturday’s fire.

“Results are still preliminary and information is still being gathered and analyzed in coordination” with Metro, an FTA spokesman said.

Saturday’s incident came amid an FTA “safety blitz” that began last month and is ongoing. Federal investigators’ initial findings showed the transit agency, among other things, is failing to provide basic safeguards, such as working fire extinguishers and clear escape routes, to help riders in the event of an emergency evacuation.

Saturday’s incident also came on the heels of an unprecedented 24-hour shutdown of the system to inspect 600 “jumper cables” — which are meant to carry electrical current between gaps in the third rail — amid concerns about their safety and reliability. Two days before the shutdown, a fire erupted near McPherson Square ahead of the morning commute, leading to nightmarish waits for thousands of riders.

Evans said he saw tweets and news reports Saturday from distraught passengers, some of whom complained about the agency’s poor communication with riders during the latest incident.

“My question on this incident is ‘Was the protocol that you drill for handled properly?’ ” he said. “Why are we always in a panicked situation when it happens?”

He said he would seek answers from Metro General Manager Paul J. Wiedefeld this week.

On Sunday, passenger Sarah Alaoui, of Northeast Washington, described a chaotic scene aboard the Red Line train. She said passengers began wondering what was wrong after the train idled for 10 minutes. A Metro employee wearing a yellow vest walked through her car, she said, and urged passengers to “move to the back.”

Passengers began arguing and climbing over seats as they rushed toward the back of the train, Alaoui said. Moments later, she said, she heard a loud boom followed by a “flash of fire outside,” with an orange tinge painting the tunnel walls.

“People were crying,” she said. “That’s what got people moving.”

Passengers began smelling smoke. Some put T-shirts over their faces to shield them from the “gritty, electric smoke”; Alaoui breathed through her scarf. It was only upon arriving at the Tenleytown-AU station that passengers learned what had happened.

“At one point I was trying to see if my phone was working like, ‘Oh can you call 911,’ ” she said. “There was no service.”

The train crawled back to the Tenleytown station, where passengers evacuated to the platform.

“It was like chaos, and nobody knows what’s going on,” Alaoui said. “Who knows what’s going to happen to you in a sealed off Metro in the tunnels when you hear an explosion? There was no information.”

Another passenger, Michael Horecki, 26, of Bethesda, said he and some visiting relatives had just strolled past the White House when they boarded a train at Farragut North en route to Bethesda. He was with his wife, sister-in-law, her husband and 4-year-old niece, visiting from Carbondale, Ill.

“We finished showing them the city, all the monuments, we walk around the Capitol and of course the [tracks] catch on fire,” he said.

Sitting toward the back of the train, they didn’t see fire or smell smoke, but panicked announcements over the intercom made passengers tense, he said. Dozens of riders crammed into two railcars at the back of the train, he said, making it feel similar to the Red Line during rush hour.

“The operator doesn’t sound super reassuring, she’s under an immense amount of stress,” he recalled. In a video Horecki recorded during the incident, a distraught Metro worker addressed passengers 10 minutes after the train stopped, saying over the intercom: “It’s very important! Please close all doors between cars!”

Another passenger Saturday described a thin haze of smoke in her northbound train while it was on its way from Tenleytown to Friendship Heights. She said she could smell smoke in the fourth car of the train.

The smoke, according to the D.C. Fire and Emergency Medical Services Department, was centered on an insulator on fire at the platform. Insulators prevent current from leaking from the third rail, which carries the electricity that powers the trains. Dirt, moisture or structural damage to the insulators can degrade their capacity to block the flow of current. As electricity begins to push through the insulator, it produces heat, smoke and sometimes fire in what is described as arcing.

Arcing insulators have been a persistent problem for the system. Earlier Saturday, an arcing insulator reported near the Bethesda Metro station led to single-tracking.

Mary Sue Burnett said Sunday that the fire forced her to disembark at Van Ness-UDC, adding an hour to the commute to her home near Rock Creek Park, as she scrambled to figure out where to hop on the shuttle buses.

The latest service disruption, however, didn’t come as a surprise to her. Like many riders, she has come to expect them.

Burnett, 51, said Metro is her only option because she doesn’t have a driver’s license, and that she has been docked at work for being late because of Metro delays.

“This year is working out to be just as bad as last year was,” Burnett said Sunday while she waited for a Red Line train from Friendship Heights to her department store job in Tysons Corner. “I don’t have any illusions about things improving.”