Photo by Rolando Pujol

Last night around 7:15 p.m. all MetroNorth trains came to a halt due to what was being called a "signal problem." Passengers were stuck on trains for nearly two hours, and Grand Central filled up with would-be passengers waiting for the trains to work again. Officials have now announced the real cause of the problem: workers disconnected a power supply to the railroad’s control center. D'oh!

According to the WSJ, not realizing a main supply unit was already disconnected, workers disconnected "one of the two main power supply units that provide electricity to the control center, the computerized heart of the railroad, where controllers monitor and protect the movement of trains across the 384-mile rail network."

Thomas Prendergast, chairman of the MTA, apologized in a statement released today that “last night’s failure was unacceptable, pure and simple. The project should have been analyzed for risks and redundancy before it began, and it should not have been performed when thousands of customers were trying to get home in cold weather.” He added that over 50 trains were stopped due the mistake, however, "all trains had light, heat and power during the disruption, and no customers were ever in danger."

While most passengers were moving again by 9:45 p.m., "full control" was not regained until 10:30 p.m.