A team of federal investigators headed to the site of a commuter train crash in Connecticut that sent dozens of people to the hospital, some in critical condition.
Officials from the National Transportation Safety Board are visiting the site of the crash on Saturday morning, the agency said.
About 70 people were injured when an eastbound Metro-North train derailed and hit a westbound train in southern Connecticut, throwing passengers around and shutting down service between Boston and New York City.
"At this stage, we don't know if this is a mechanical failure, an accident or something deliberate," Fairfield police spokesman Lt. James Perez told the Connecticut Post.
Gov. Dannel Malloy told reporters Friday night that five people were "critically injured," one of whom was in "very critical condition."
More from GlobalPost: Connecticut commuter trains collide, dozens injured (VIDEO)
By Saturday morning, 46 of the 70 people who had gone to hospitals have been released.
The condition of one of the critical patients at Bridgeport Hospital has also been upgraded to fair, hospital spokesman John Cappiello told CNN.
"We're most concerned about the injured and ultimately reopening the system," Gov. Malloy told reporters Friday night from the crash site.
Malloy said US Sens. Richard Blumenthal and Chris Murphy and other Connecticut officials would be joining him Saturday morning to survey the site of the accident.