An electric line was torn down, and power was cut to the area while the line was repaired.
Amtrak spokeswoman Tracy Connell said investigators were trying to determine the origin of the damage that the engineer reported.
Morning commuters on the Metro-North Commuter Rail from New Haven, Milford, and Stratford, Conn., were bused to Bridgeport to catch their trains.
The accident limited Amtrak service to the region for several hours.
Five trips were canceled, and others were delayed.
Amtrak stopped some northbound passenger trains in New York City and bused passengers to New Haven, where they waited for service to resume.
By yesterday afternoon, trains were operating with about a half-hour delay.
Officials said they expected a relatively normal evening commute.
Susan Birnbaum of Philadelphia boarded an Amtrak train in Trenton, N.J., to go to Cambridge, Mass., to visit her son, a freshman at Harvard.
"It's my first time traveling on a train and I think it's my last. I'm disgusted," said Birnbaum, who spent part of the night in Pennsylvania Station in New York.
Another passenger, Rachel Buske of Washington, D.C., hunkered down at New Haven's Union Station wearing a Boston Red Sox cap and sweatshirt and a very long face.
"I was trying to get to Boston. I was trying to get to the World Series parade," she said.
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