NJ Transit spokesman Jim Smith said Northeast Corridor train #3926 that left Trenton at 7:30 a.m. was involved in a "slow speed derailment" on track #9 around 9 a.m.
An NJ Transit derailed at New York Penn Station on Monday morning.
The LIRR said it will cancel 18 trains out of Penn between 4 and 8 p.m., and will have eight others originate at Atlantic Terminal or Jamaica.
NJ Transit reported that one person sustained minor injuries, and emergency personnel was still on the scene.
NJ Transit says it has service suspensions and delays.
It wasn't immediately clear why the train derailed, but fire officials said one of the wheels was missing on an affected train.
About 1,200 passengers were on the train at the time.
Acela service on the Acela Express and Northeast Regional lines will be delayed between Newark and NY.
The derailment comes just a week and a half after an Amtrak Acela train derailed at Penn Station, causing some service disruptions.
The Long Island Rail Road is anticipating a slew of delays and cancellations during the evening rush hour. It scraped the side of an arriving NJ Transit train on March 24th. Investigators from the Federal Railroad Administration are en route to Penn Station.