WASHINGTON » The rail system that serves the nation’s capital and its Virginia and Maryland suburbs will shut down for a full day after a fire near one of the system’s tunnels, the system’s general manager announced today, posing a potentially disastrous commute for hundreds of thousands of workers in the federal government and private sector alike.

The system will be shut down all day Wednesday for an emergency inspection of its third rail power cables, General Manager Paul J. Wiedefeld told a news conference at the agency’s headquarters.

“While the risk to the public is very low, I cannot rule out a potential life safety issue here, and that is why we must take this action immediately,” Wiedefeld said.

Metro is the nation’s second-busiest transit network, serving more than 700,000 riders daily, and a vital link for federal workers and other commuters to Washington from Maryland and Virginia. The system will shut down at midnight tonight and remain closed until 5 a.m. Thursday, a total of 29 hours.

D.C. Councilman Jack Evans, the chairman of Metro’s board, said that while the system had previously been closed for days for weather, including earlier this year, it was believed to be the first time the system had shut down for mechanical reasons.

A fire on the tracks led to major delays throughout the system on Monday. The fire was caused by the same kind of electrical component that malfunctioned last year and caused a train to fill with smoke inside a downtown Washington tunnel, killing one passenger and sickening dozens.

During the shutdown, Wiedefeld said that about 600 so-called jumper cables will be inspected throughout the system. Wiedefeld said those cables were inspected after the L’Enfant Plaza fire and deficient ones replaced.

Rep. Gerry Connolly, a Virginia Democrat, called on the U.S. Office of Personnel Management to allow federal workers to take unscheduled leave or telework on Wednesday, calling the decision to shut down “a gut punch to the hundreds of thousands of commuters who depend on the system.”

“While I am extremely frustrated with this news, safety must be our No. 1 priority,” Connolly said in a statement. “This dramatic action highlights the need for long-term safety and reliability improvements throughout the system.”