ELIZABETH, N.J. (AP) — A suspicious device found in a trash can near a New Jersey train station exploded early Monday as a bomb squad was attempting to disarm it with a robot, officials said.

Elizabeth Mayor Christian Bollwage said that the FBI was working to disarm one of five devices found in the same bag, which was discovered in a trash can by two men around 8:30 p.m. Sunday, near the Elizabeth train station on New Jersey Transit's Northeast Corridor rail line. The men had reported seeing wires and a pipe coming out of the package, Bollwage said.

There was no immediate report of injuries or damage. A message left with the FBI wasn't immediately returned. The mayor warned that other explosions were expected.

NJ Transit service was suspended early Monday between Newark Liberty Airport and Elizabeth, and New Jersey-bound Amtrak trains were being held at New York Penn Station, officials said, while New York-bound Amtrak trains were being held in Trenton.

Train passengers reported being stuck on Amtrak and NJ Transit trains for hours Sunday night, while some trains moved in reverse to let passengers off at other stations. Amtrak said 2,400 passengers were affected and that trains were being brought into other stations for people to get other transportation. It wasn't clear when the Elizabeth station would be open, a threat to cause major issues on the Monday morning commute into New York.

The discovery of the suspicious package comes a day after an explosion in Manhattan injured 29 people, and an unexploded pressure-cooker device was found four blocks away. Also Saturday, a pipe bomb exploded about an hour from the Elizabeth train station in Seaside Park, New Jersey, forcing the cancellation of a military charity 5K run. Officials said it didn't appear that those two incidents were connected, though they weren't ruling anything out.

Investigators didn't immediately comment on whether they thought the Elizabeth incident was connected to either of the two blasts.

Bollwage said that he wasn't willing to say that Elizabeth had become a target, and that it was possible that someone worried about the authorities was trying to get rid of the package.

"I'm extremely concerned for the residents of the community, but more importantly extremely concerned for everyone in the state and country where someone can just go and drop a backpack into a garbage can that has multiple explosives in it with no timers and then you have to wonder how many people could have been hurt," Bollwage said.