Approximately 60 people were taken to hospitals this evening - five with critical injuries - when a New York-area commuter train derailed near Fairfield, Conn., knocking a second train coming the other way off the tracks, officials said.

Amtrak train service between New York and Boston was suspended indefinitely, as was service on the Metro-North Railroad's New Haven commuter line in Connecticut, amid an investigation.

Officials said two of four tracks in the area were already out of service for extensive maintenance work on overhead wires, and the other two tracks and overhead wires were damaged during the collision of the Metro-North Railroad commuter trains.

Connecticut Gov. Dannel Malloy estimated normal service would not resume until at least Monday.

"These tracks have been torn up," he told reporters. "There's been extensive damage."

(Christian Abraham/The Connecticut Post via AP Photo)

The National Transportation Safety Board was sending a team to investigate the crash, and was to be the lead agency in the investigation.

Local police initially put the number of injured between 20 and 25, but several hours later Malloy said 60 people had been taken to hospitals. Five of those 60 had critical injuries, he said, including one person who was considered "very critical."

The accident occurred just east of the Fairfield metro station at approximately 6 p.m., when trains heading in opposite directions between New Haven, Conn., and New York's Grand Central Terminal collided, officials said. The collision occurred after the derailment of the New York-bound train carrying an estimated 300 people. That train hit the other train, carrying an estimated 400 people, knocking it off the tracks.

Rob Oliver, a passenger on board the train that was struck, said he heard "a tremendous amount of metal and just an extremely loud sound."

"We suddenly were screeching to a stop, but you knew it wasn't a screech-normal stop … because there was just an awful burning smell and the cabin was filling with smoke," he said.

He saw people being removed on stretchers with apparent neck or back injuries.

"I know some people breathed in some smoke, including myself, and I'm sure there's people who have those sorts of [smoke] injuries," he said. "Other people got injured coming off the train, because it's a big jump down to the tracks and people were scrambling to get off the tracks as quickly as possible."

Multiple reports of injuries initially prompted officials to scramble ambulances from all over the region to the site, police said.

The train cars involved were M8s, which were fairly new to the New Haven line. This was the first serious accident involving the new cars, considered state-of-the-art.

ABC News' Howard Price contributed to this report.