The incident came after the United States was shaken by three attacks over the weekend, including a Saturday night bombing that injured 29 in Manhattan and a stabbing incident at a Minnesota shopping mall that wounded nine.
In Elizabeth, a city south of Newark, New Jersey, two men scavenging trash near the train station on Sunday evening found a suspicious package containing what could have been a live bomb in a trash can, Mayor Christian Bollwage said.
The men reported the package to police after they "saw wires and a pipe," Bollwage told reporters. A Union County bomb squad drone determined the package "could be a live bomb" and an FBI bomb squad went to the site.
A large explosion was heard early on Monday near the transit station, NBC News reported. On social media network Twitter, Bollwage confirmed that police had detonated the suspicious package. In a subsequent tweet, he confirmed that the explosion followed a police bomb robot's attempt to disarm the device.
An FBI spokesman in Newark, Mike Whitaker, said agents were aware of the situation in Elizabeth. "We are responding with our local law enforcement partners," he added, but declined to give further details. 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.
New Jersey Transit Corp and Amtrak halted train services to the Elizabeth station as investigations continued, authorities said.
A powerful explosion rocked Manhattan's popular Chelsea neighborhood late on Saturday after a pressure-cooker bomb packed with shrapnel detonated. A similar unexploded device was found a few blocks away later that night.
The Chelsea blast followed a pipe bomb explosion on Saturday morning along the route of a running race in the New Jersey beach town of Seaside Park. No one was injured in that blast, which is being investigated.
Police in Union County, New Jersey, declined to comment.
The Associated Press also contributed to this report