Service on several of the New York area's vital rail lines was restored in time for Monday's commutes, a day after a derailment and a crash threatened to wreak havoc at the beginning of the work week.

Still, the nation's largest commuter railroad said that commuters should expect significant schedule changes the next few days during work to repair a track that apparently caused an empty Amtrak train to derail late Sunday.

Meanwhile, authorities investigated the cause of Sunday's commuter train crash in New Jersey while police said it appeared that mechanical failure was to blame. More than 30 people were injured in the crash, none seriously.

Most area transit agencies honored one another's tickets Monday, and additional buses and ferries were added to relieve some of the burden.

"I probably got here 16 minutes later than I expected to," said Nick Guldi, arriving in the morning at Penn Station in Manhattan from Bellmore, on Long Island. "That means I won't be able to walk to work. I'll have to take the subway."

Any problem along the New York-area rail network has the potential to disrupt trains that shepherd hundreds of thousands of people daily to and from the city and connect them to the subway or other regional rail systems, often through Penn Station, the nation's busiest train depot.

On the east side of Manhattan, under the East River separating it from Long Island, the Amtrak train that derailed because of track damage caused minor commuting headaches on the extensive Long Island Rail Road.