An electrical malfunction and smoke in a Metro tunnel under the Potomac caused an hours-long suspension of service Monday on a bottleneck stretch of three rail lines, stranding thousands of morning commuters and raising howls of protest over another breakdown of the Washington area’s transit system.

A second significant disruption occurred late Monday night at another of the rail system’s choke points when Metro Center was closed to passengers. As basketball fans were leaving the Verizon Center, smoke was reported in the tunnel and power was said to be cut off. Trains on the Blue, Orange and Silver lines passed through on one track, causing delays on those lines. Although Red Line trains also did not stop, they were said to be running without delays.

The District’s AlertDC system said the problem was caused by a transformer and was under control by 11:02 p.m.

Earlier Monday, in a situation similar to one that turned fatal in a Yellow Line tunnel Jan. 12, electricity that is used to power trains began escaping from the inbound third rail on Metro tracks under the Potomac about 8 a.m., the transit agency said.

Although there was no fire, Metro said, the electricity, which is supposed to be safely contained within insulation, generated heat and smoke as it escaped in the tunnel between the Rosslyn and Foggy Bottom stations. Four months after scores of Yellow Line passengers were sickened in a smoke-filled tunnel near the L’Enfant Plaza station, and one rider died, Metro reacted Monday by immediately shutting down a major part of the rail system.

Metro riders stuck at D.C.'s Rosslyn station lament their massively delayed morning commutes. (WUSA9)

Orange and Silver line trains headed for the District were halted at the Clarendon station, west of Rosslyn; District-bound Blue Line trains were stopped at the Arlington Cemetery station, south of Rosslyn; and Orange, Silver and Blue line trains traveling to Virginia from the District were allowed to go no farther than Foggy Bottom. Exasperated riders were taken off trains and stood in blocks-long lines, waiting for shuttle buses.

While firefighters and Metro workers dealt with the smoke problem, service through the subway choke point beneath the Potomac, between Rosslyn and Foggy Bottom, was shut down for more than three hours, before resuming at a limited pace about 11:15 a.m., Metro said.

Full service was not restored until shortly after 2 p.m., by which time thousands of angry commuters, mostly on the Virginia side of the river, had been inconvenienced for hours.

Then just before 5 p.m., a track switch at Stadium Armory stopped working properly, delaying service on the same three lines during the evening rush.

The disastrous morning commute prompted an apology from Metro officials.

“Please know that the actions taken this morning were with your safety as our highest priority,” Mortimer L. Downey, chairman of Metro’s board of directors, said in an apology to riders that was posted on the agency’s Web site Monday afternoon. “Despite the fact that there was no significant smoke in any station, Blue, Orange and Silver line service was suspended between Rosslyn and Foggy Bottom out of caution.”

Metro passengers move toward buses outside the Foggy Bottom Metro station on Monday to take them to Rosslyn. (Andrew Harnik/AP)

In an interview, Downey said the problem involved “insulators,” small stanchions that isolate the electrified third rail from the track bed. There are thousands of them in the system, and conducting substances sometimes cause them to degrade and begin to conduct electricity, permitting current to escape the third rail and reach the ground. Heat and smoke are generated in this “arcing” process.

Metro’s apology came long after riders had vented their frustrations. For thousands of commuters stuck in Virginia — waiting for buses and fretting about their work at the start of a new week — frustration with the transit agency was immense, including anger over a dearth of information coming from officials. Many riders said Metro employees had no information about what was going on and offered little direction to customers.

One of the riders’ persistent complaints is the agency’s seeming inability to communicate clearly with the public. And Monday offered a prime example.

“It is an absolute nightmare,” said John Bevir, a British TV cameraman. He said he left his home near the Virginia Square Metro station in Arlington and got stuck in the morning mess. In frustration, he walked three miles from Virginia Square, across the Memorial Bridge, to a spot near the White House where he was scheduled to do a video shoot. He said 60 to 70 other stranded Metro users hoofed across the bridge with him.

His trek downtown, which normally takes minutes, lasted more than two hours, he said.

“I walked past six bike racks, and there wasn’t a single bike in any of them,” Bevir said, referring to the Capital BikeShare stations. “I haven’t yet seen a taxi that wasn’t full, and there were 300 people trying to get on a bus at the Rosslyn stop.” Walking along M Street NW in Georgetown, he said: “There was just no other option.. . . The lack of information has made this spectacularly difficult.”

Anger among commuters lit up Twitter. “More than 2 hours after I left my house in falls church,” one user wrote just after 9:30 a.m., “I’ve finally arrived at federal center. Hellish day on metro.” Tweeted another: “Empty train. Overcrowded platform. Zero instructions. Banner morning.” And another: “It’s like the apocalypse in Rosslyn this morning.”

As riders exited trains, they headed not only for buses, but for taxis. And they called Uber, which appears to have benefited from the extended delays. There were reports of major price surges for the service — in at least one case, almost five times the regular cost.

In Clarendon at one point, the line of people waiting for shuttles stretched for blocks at North Highland and 11th streets near the station. Among the scores of commuters shuffling along was Jennifer Robbins, a Capitol Hill lawyer who lives in Fairfax.

“What do I think of Metro? Not much!” said Robbins, 52.

Farther back in line, a young woman on a cellphone yelled to the crowd: “I got a ride to Foggy Bottom! Anybody want to come?” But Robbins stayed put. “I’m sure they’re going to say it’s budget cuts and they’re doing the best they can. But it’s certainly not good enough on a day like this.”

Paul Goodman became so aggravated with the wait at Ballston that he gave up. The limited shuttle buses provided by Metro were too crowded. So he walked to his office near Foggy Bottom.

“There was no information,” he said. “It is extremely frustrating. The rates go up, and the service goes down.”

In an interview, Downey said that while investigating the morning incident, Metro workers discovered that several third-rail insulators in the tunnel “were showing signs of electrical sparking.” He said that all were replaced by early afternoon. In his apology letter, he said parts had to be brought to the tunnel from Maryland, “further contributing to the length of our response.”

Electrical arcing also caused the incident in January, according to the National Transportation Safety Board, which is still investigating.

“There are a couple of things that concern me,” Downey said. “One is, how good a job we’re doing in the [Rail Operations] Control Center with respect to getting information out to the public. That’s clearly something we need to continue looking at, to see what can be done.”

He said: “The other issue is, it’s clear that there has been, I think, a significant uptick in arcing insulators. We were told that there’s an issue that has to do with steel dust in the tunnels. Steel dust, when it accumulates on an insulator, can cause electrical current to move outside where it’s supposed to be.”

Getting rid of the steel dust “isn’t easy,” he said. “There’s an inability to wash the tunnels because of new environmental discharge regulations, and that has been a problem. We’re told they’re working on a fix for that.”

As for changes made in Metro’s protocols for dealing with smoke and how they were involved Monday, Metro spokeswoman Morgan Dye said transit officials would not publicly discuss the issue until Thursday, when they will make a presentation to the agency’s board of directors.

“I don’t know specifically yet what the new orders are,” Downey said. “But I’m reasonably sure that people are very cautious about moving any train near any kind of smoke environment.”

Martin Weil and Julie Zauzmer contributed to this report.