BRIDGEPORT -- All Metro-North trains across New York and Connecticut were stopped in their tracks for about two hours Thursday night and some on the Danbury branch remained stuck even longer because of a power disruption to the computer system used to control the trains.

The computer problem at the railroad's headquarters in Grand Central Terminal happened at 7:45 p.m., leaving thousands of passengers stranded across the tri-state area. Passengers were told to seek alternate transportation from train stations.

At 9:45 p.m., Metro-North reported that the Harlem, Hudson and New Haven lines were back in service, although riders faced significant delays.

Metro-North spokeswoman Marjorie Anders said trains remained stopped on the Danbury Branch at the Branchville, Redding and Bethel stations, and that it was taking longer to get those trains back into service. Service on the Danbury Branch was reported restored around 12:25 a.m.

She said the systemwide disruption remains under investigation.

"We don't know the source yet," Anders said. "It's a localized issue. The terminal didn't have a blackout. The control room didn't have a blackout. We had a power issue to the computer. So we're not pointing fingers at Con Ed now."

Anders told News 12 Connecticut that temporary power was brought in "like a big extension cord" to restore the system.

She said she didn't think the power interruption would affect the morning commute, but the cold might.

"When it gets cold, we slow down because the (overhead) wire's brittle, the rails are brittle," Anders said. "The colder it gets, the more we decrease our speed."

Only the night before, on Wednesday, overhead wires near Westport broke and stalled a train for two hours, stranding more than 200 passengers.

During Thursday night's stoppage, Bridgeport resident Antonio Bennett, who works in Greenwich, was stuck there.

"You wonder what's going to happen next?" said Bennett, 54. "If it keeps going like this, I'm going to have to think about driving to work. But the train is supposedly more convenient."

U.S. Sen. Richard Blumenthal, D-Conn., said his staff had been communication with Metro-North officials about the latest service disruption, but he said they had not given him a cause.

"I've heard from some very irate stranded passengers," Blumenthal said by phone Thursday night. "This incident will understandably be seen as another sign of a broken system."

One longtime Metro-North employee, who lives in Fairfield County and spoke on condition of anonymity, said the entire system had never been shut down before, in his memory.

"This is a first," the employee said. "It doesn't make you feel good."

This story was still developing late Thursday night. Readers can visit for updated information.

Metro-North officials tried to assure the public that their staff would fix the problem quickly on Thursday.

But the shutdown was the latest in a string of high-profile mishaps the railroad has weathered in the past year in Connecticut and New York. The stretch included two derailments, at least two fatal collisions and a power outage that paralyzed service between southwestern Connecticut and New York City for days last fall.

Metro-North's infrastructure problems have drawn intense scrutiny in Connecticut, where the trains are electrically powered. When a massive power outage knocked out service on part of the New Haven Line in September, the cause was determined to be a power cable that was 36 years old. The railroad is reportedly decades behind on maintenance and would need millions of dollars to get up to speed.

In an interview Thursday with Hearst Connecticut Newspapers -- before the railroad's nighttime shutdown -- U.S. Rep. Jim Himes, D-Conn., said Connecticut is treated like an "ugly stepchild" compared to New York when it comes to service on Metro-North Railroad.

Ironically, just hours before the major shutdown, passengers were on Twitter venting about Wednesday's night's power problems, and state Sen. Toni Boucher, R-Wilton, who represents Westport, channeled their frustration. The state senator, who is exploring a run for governor, said the railroad needs new management in the form of an oversight board.

"Obviously, the people who are there lack the competence to do thing right," Boucher said.

Staff Writers Wes Duplantier, Martin Cassidy, Brian Lockhart, Rob Varnon, Neil Vigdor, Paul Schott, John Burgeson and Digital News Editor Jim Shay contributed to this report.