NEW YORK — A commuter train shook on the tracks and then derailed in a tunnel under the East River shortly after leaving Penn Station on Monday night, forcing the hundreds of passengers on it to be removed and delaying the trip home for many others. No injuries were reported.

The 5:51 p.m. Long Island Rail Road train to Hempstead, Long Island, carrying up to about 1,000 people, had been traveling slowly as it entered one of four East River tunnels, Metropolitan Transportation Authority spokeswoman Marjorie Anders said. The derailment took place around 6:10 p.m., and it was unclear what caused it.

Passenger Tameka Chandler, of Queens, said she was in the eighth of 10 cars. She said when the train got into the tunnel, it started to shake and rock and she could see the car ahead of hers tilted to one side before it derailed.

"It was sideways," she said.

The passengers remained calm, Chandler said.

"People were looking around, but it wasn't chaotic," she said.

Train employees and emergency personnel showed up soon after and helped them get off the train.

Passengers in the rear five cars walked through the train and got out, while another train was brought alongside for passengers in the front five cars to disembark, Anders said. By 8:15 p.m., all passengers had been taken off, she said.

The disabled train blocked one of four tunnels under the river, which separates Brooklyn, Queens and Long Island from Manhattan and the Bronx. The train was being removed Monday night.

There was limited eastbound LIRR service out of Penn Station, one of the nation's busiest transit hubs. Westbound service into New York City was suspended to allow trains to head east using the three remaining tunnels. By 11:30 p.m. Monday, service was restored in both directions between Penn Station and Jamaica, Queens.

The disruption also affected people trying to get to other trains, with the station limiting entrance temporarily to reduce crowding. By 8 p.m., passengers were again going in and out of the station, with those waiting for LIRR trains dealing with delays of about an hour as they tried to get home.

"I was just getting ready to sit down on the train after being on my feet all day," said Ife Oshikanlu as she waited an extra hour for the train that would get her home to Long Island's Deer Park.

Last month, a train derailment in Connecticut injured more than 70 people. The National Transportation Safety Board has said that two days earlier a track inspection found problems where the derailment occurred, just outside Bridgeport.

The Metro-North Railroad, which operates between New York City and Connecticut and like the LIRR is run by the MTA, has hired an outside firm to review its track maintenance and inspection programs.