A commuter train heading east from New York City derailed and collided with another train in Fairfield, Conn., during the busy Friday evening rush hour, injuring 60 people, including five that state officials said are in critical condition.

The accident of the Metro-North trains shut down much of Connecticut's commuter-rail service Friday evening. A spokeswoman for the Metropolitan Transportation Authority, the New York-area agency that runs Metro-North, said there was major damage to tracks and that rail service on the busy...