Gov. Dannel P. Malloy said five people were critically injured and one was very critically hurt in Friday evening's crash on the Metro-North Railroad, which serves the northern suburbs of New York City.
Passengers described a chaotic, terrifying scene of crunching metal and flying bodies.
"All I know was I was in the air, hitting seats, bouncing around, flying down the aisle and finally I came to a stop on one seat," Lola Oliver, 49, of Bridgeport, told The Associated Press. "It happened so fast I had no idea what was going on."
About 700 people were on board the Metro-North trains when one heading east from New York City's Grand Central Station to New Haven derailed about 6:10 p.m. just outside Bridgeport, MTA and Bridgeport officials said.
The train was hit by another heading west from New Haven to Grand Central on an adjacent track, MTA spokesman Aaron Donovan said. Some cars on the second train also derailed as a result of the collision.
The nursing supervisor at St. Vincent Medical Center said early Saturday that more than 40 people had been seen and that five patients were remained there, including one in critical condition.
Bridgeport Hospital spokesman John Cappiello said that as of 0600 GMT Saturday about 14 people were still being seen and that two patients were in critical condition.
Malloy said there was extensive damage to the train cars and the track, and it could take until Monday for normal service to be restored. Amtrak, which uses the same rails, suspended service indefinitely between New York and Boston.
Investigators Friday night did not know what caused the first train to derail. Malloy said there was no reason to believe it was anything other than an accident. The National Transportation Safety Board was sending a team to investigate.
The area where the accident happened was already down to two tracks because of repair work, Malloy said. Crews have been working for a long time on the electric power lines above the tracks.