There were signs in recent weeks that Metro was on the upswing, helping the Washington region bounce back from a pandemic that kept workers away from the city’s core and off public transit.

Rail riders who mostly stayed away as the virus spread were coming back, heading into offices while also lifting Washington’s sagging downtown economy. But after last week’s Blue Line derailment triggered a federal safety investigation and the removal of more than half the agency’s rail fleet from service, officials worry about damaging a fragile recovery.

The safety lapse is the largest Metro has faced since smoke poured into a stalled train outside L’Enfant Plaza in 2015, killing a passenger and injuring dozens more. The public confidence the transit agency has tried to rebuild in the years since is in danger of evaporating despite hundreds of millions of dollars spent to improve safety on the system.

The longer that lower service levels persist, the more likely Metro is to face lasting repercussions financially, politically and in the perception of riders, according to customers and U.S. Rep. Gerald E. Connolly (D-Va.), whose influence and advocacy has helped boost Metro funding over the years.

“It’s a continual drip, drip, drip in the number of safety-related problems that seem to be admitted only belatedly, and all of that erodes confidence,” said Connolly, chair of the House Government Operations subcommittee, which required Metro status reports after the 2015 incident. “And it’s compounded by the fact that we’ve already lost ridership, big time, because of the pandemic and because of our federal government basically working remotely. So to try to win back the public ridership while also having a crisis of confidence in the safety of the system, the reliability of the system — and for that matter, the credibility of communication from the system — is like a perfect storm for Metro.”

Neil Albert, president of the DowntownDC Business Improvement District, said Metro is vital to the city’s office workers, who in turn drive the retail and dining economies.

“Any major interruption to a recovery is bad timing,” Albert said. “Metro is a big part of downtown and D.C.’s resiliency. As Metro’s own numbers suggest, things were trending in the right direction. I’m hoping this does not take forever to get back to normal service.”

But Metro has yet to provide much clarity. A long spell of the pared-back rail service that Metro is offering — trains every 30 minutes on most lines using 1980s-era cars — could lead people to turn their backs on the nation’s third-largest transit system at the moment many were ready to ride again.

Metro Board Chairman Paul C. Smedberg said the transit agency’s leadership will take action to enhance rider confidence as it learns more about Metro’s inspection processes of rail cars, which is under scrutiny, and as more is known about the National Transportation Safety Board investigation.

“Metro has to earn rider confidence every day,” Smedberg responded in a statement that italicized those two words. “That includes satisfying public health concerns in a pandemic, and it includes demonstrating that we operate equipment safely.”

He continued: “It is crucial that the riding public and our stakeholders continue to have confidence in the safety of the system for Metro to fulfill its role for the region.”

Metro announced late Sunday it was pulling all 748 of its 7000-series cars from service because of a defect in the wheel assemblies of several cars. The NTSB, which is leading the investigation into the derailment, said wheels on a car that came off the tracks last week had shifted outward on their axle.

Inspections have revealed dozens of similar defects, which NTSB Chair Jennifer Homendy said had the potential to be catastrophic. The problems had not been disclosed to the public or safety regulators but were first detected by Metro as far back as 2017.

Del. Eleanor Holmes Norton (D-D.C.), who chairs a subcommittee on highways and transit that oversees Metro, said she expects to soon hold a hearing on the derailment and the investigation.

“What particularly concerns me is that it looks like these issues were well-known at least since 2017,” she said. “If this was the first time the issue had been raised, I could understand it. These issues are almost four years old now.”

The transit agency has said that when it detected problems with wheel assemblies in the past, it pulled trains from service and replaced them. But the problem appeared to be getting steadily worse, according to data the NTSB released Monday, and a fresh round of inspections launched after the derailment revealed 21 more failed axles.

Kawasaki Rail Car, which makes the 7000-series cars at a plant in Nebraska, has not responded to multiple requests for comment. The cars entered the system between 2015 and 2020.

The transit system’s 6000 series, about 15 percent of its fleet, has also been sidelined since November after two train separations on the Red Line.

Metro has said it expects the reduced service level to continue at least through Sunday. But it hasn’t spelled out what it will take to bring the cars back into service, leaving riders and regional leaders concerned about a lengthy disruption, as well as frustrated with what some said was inadequate communication during a crisis.

Metro General Manager Paul J. Wiedefeld and board members have communicated via statements to the public. The NTSB restricts agencies involved in the investigation from releasing information on the probe but doesn’t limit what Metro can say about service plans.

“What is the plan here? What went wrong? How did it go wrong?” Connolly said. “How did you miss it, or did you miss it and not tell us? And what are the corrective steps, the remediation measures you’re taking to ensure that this is fixed and not repeated?”

D.C. Council member Mary M. Cheh (D-Ward 3) urged Metro to be transparent with the public and communicate its recovery plans clearly.

“If they can get these cars back into service in a week, I think we could regain the traction that was there,” she said. “If it’s longer than that, people may start to think about alternatives.”

D.C. Council member Charles Allen (D-Ward 6) said Metro appeared to be putting riders’ safety first, an approach he said might limit harm to the public’s confidence in the agency. He said he’s heard from constituents who are ready to board trains.

Andrew D. Realon, who said he was on the derailed train, said he hadn’t had communication with Metro until Tuesday, when he got a call offering him a $21 credit as compensation — an offering he said he took as an insult.

“The most frustrating thing about the experience was the lack of information,” Realon said.

Metro spokeswoman Sherri Ly confirmed the agency gave passengers on the train the compensation “to offer an apology along with this small gesture of appreciation.”

Realon said that, with the reduced train service, he has been driving to work, paying more to park than he would spend on fares. Crowding on trains and at stations worried him during the pandemic, he said.

The lower service levels are coming months after Metro’s board approved service increases and fare reductions as part of a campaign to lure riders back from the pandemic slump.

Metrorail had seen steady growth in passenger counts in recent weeks. Metro averaged 213,250 daily passenger trips on weekdays last week — excluding the Monday holiday — which is more than 40 percent higher than four months earlier.

To Albert, that rise translated into the beginnings of a recovery for downtown that suddenly has become more in flux.

“We have been seeing an upward trend in all of the key economic indicators in D.C. over the last month or so,” he said. “While there’s still a long ways to go, we were seeing signs of progress.”