In an email, Metro General Manager Paul J. Wiedefeld said seven of the 20 fired managers were senior managers, and more than one-third worked in subway operations. (Andrew Harnik/AP)

Metro fired 20 managers Friday in what the agency’s top executive described as a step toward “restructuring” the Washington Metropolitan Area Transit Authority after months of subway safety problems, service disruptions and financial woes.

General Manager Paul J. Wiedefeld sent an email to Metro employees announcing the firing of the managers, seven of whom he identified only as senior managers. More than one-third of the fired managers worked in subway operations, Wiedefeld said.

The firings were “immediate, effective today,” Metro spokesman Dan Stessel said Friday. The 20 managers were among about 650 “at-will” employees of the transit agency, meaning they could be let go at the general manager’s discretion.

Wiedefeld, hired as Metro’s general manager and chief executive in late November, has vowed to streamline the organization, which employs about 13,000 people, a vast majority of whom are members of three labor unions.

Metro declined to specify what departments the fired managers worked in or what any of the managers’ individual job responsibilities were. “I hope you will join me in respecting the privacy of these individuals, and note that I will not be commenting about individual employees,” Wiedefeld told the agency’s workforce in the Friday email.

After decades of maintenance neglect, the 118-mile subway system has been chronically beset by safety-related infrastructure problems, especially over the past year and a half, with electrical-related track fires becoming common. In October, Metro became the only big transit agency in the nation to be placed under federal safety oversight.

Meanwhile, an array of the agency’s financial problems have come to light, stemming from Metro’s mismanagement of federal grant money and from a decline in operating revenue partly caused by a steady drop in subway ridership.

As Wiedefeld struggles to revitalize the agency, officials across the region, including members of Congress, have demanded that he do more to hold Metro managers accountable for the problems and fire those who fail to perform.

Friday’s personnel action comes less than two weeks after Wiedefeld addressed an unprecedented gathering of Metro’s approximately 650 at-will employees, held May 10 at the Strathmore concert hall in Rockville, Md.

Officials said the purpose of the gathering was for Wiedefeld to formally introduce himself to the hundreds of managers and explain his vision for the transit agency, including his goal of developing a robust institutional safety culture and his intention to hold employees accountable for Metro’s shortcomings.

Rep. Gerald E. Connolly (D-Va.), a longtime supporter of Metro, yet one of its toughest critics on Capitol Hill, has been among those calling for heads to roll at the transit agency. He applauded Wiedefeld’s decision Friday.

“People have to be held accountable,” Connolly said. “The Metro general manager has been urged to do that. I hope this sends a signal across the entire Metro organization that safety and customer service must come first.”

Another frequent Metro critic, Sen. Benjamin L. Cardin (D-Md.), echoed Connolly.

Citing the transit agency’s “years of neglectful decisions and a failure to confront problems,” Cardin said Wiedefeld “is taking decisive action that demonstrates a strong commitment to safety and the important tasks ahead of him.”

Besides the managers in subway operations who were let go, “others are in administrative areas, including procurement,” Wiedefeld said in his email, without elaborating on specific jobs. He said the personnel moves were meant to “improve effectiveness and accountability” in the agency’s management ranks.

Asked if the firings were based on individual job performances, Stessel said: “No. These are at-will employees being released as part of a restructuring.”

But he added: “That said, recently [Wiedefeld] did approve a handful of terminations for cause. And in addition to that, there are a number of employees here who are on ‘performance plans,’ which are our last-chance mechanisms. And, frankly, some of those employees will likely be separated from the organization, as well.”