Metro computer malfunction?

Yesterday, there was a tragic crash on the Washington DC Metrorail system. It killed nine. Tonight, there are indications that computer malfunction may have been at least partly to blame. From Associated Press (h/t Drudge Report):

WASHINGTON – Investigators looking into the deadly crash of two Metro transit trains focused Tuesday on why a computerized system failed to halt an oncoming train, and why the train failed to stop even though the emergency brake was pressed.

At the time of the crash, the train was also operating in automatic mode, meaning it was controlled primarily by computer. In that mode, the operator's main job is to open and close the doors and respond in case of an emergency.

I took Metro to work today, and it was somewhat surreal to hear the PA system announcer gingerly refer to "a situation" at the Fort Totten station requiring the use of shuttle buses and an extra hour of travel time for affected Red Line passengers.