Explosive devices were found inside a bag in a trash can near New Jersey's Elizabeth train station. One of the five devices exploded while a bomb squad robot was attempting to disarm it.
Investigators on Sunday probed three attacks carried out on US soil — a bombing in Manhattan, a mass stabbing in Minnesota and a pipe bomb blast in New Jersey — for possible terror links, as five people were reportedly detained in New York.
Authorities say there is no evidence that the attacks were coordinated but their timing in less than 24 hours has raised fears over security — already a major issue in the country's divisive presidential election battle between Hillary Clinton and Donald Trump.
Late on Sunday, rail services in New Jersey state was suspended between Newark airport and the city of Elizabeth after a suspicious package was found near the Elizabeth train station.
Elizabeth Mayor Christian Bollwage said a suspicous bag was found in a trash can by two men who reported seeing wires and a pipe coming out of the package. Five improvised explosive devices (IED) were later discovered to be in the bag.
One of the devices exploded as a bomb squad used a robot to disarm it. No injuries were reported.
New York went on full alert on Sunday, deploying nearly 1,000 extra state police and National Guardsmen to airports, bus terminals and subway stations as US President Barack Obama arrived in the city ahead of Tuesday's opening of the UN General Assembly.
New Yorkers will see more heavy weapons teams at events citywide. And in subways in addition to bag checks, @NYPDChiefofDept says— J. Peter Donald (@JPeterDonald) September 18, 2016
Earlier on Saturday night, Twenty-nine people were injured when a bomb exploded in New York's upmarket Chelsea neighbourhood damaging buildings, shattering glass and sending shrapnel flying across the street.
A second bomb was uncovered by police four blocks away and defused safely before being sent to the FBI in Virginia for forensic examination.
Both bombs were filled with shrapnel and made with pressure cookers, flip phones, Christmas lights and explosive compound, The New York Times reported late on Sunday, citing law enforcement officials.
A similar sort of IED had killed three people and wounded more than 260 in the 2013 Boston Marathon bombing.
The paper also said, citing unnamed law enforcement sources, that federal authorities detained and were questioning five people with possible links to the New York bombing.
The FBI's New York branch tweeted that officers "did a traffic stop of a vehicle of interest" but "no one has been charged with any crime."
We did a traffic stop of a vehicle of interest in the investigation. No one has been charged with any crime. The investigation is continuing— FBI New York (@NewYorkFBI) September 19, 2016
The New York Daily News reported that weapons were found in the car.
The FBI's New York branch also tweeted the picture of a suspect identified as Ahmad Khan Rahami.
A statement by the FBI said that the 28-year-old Afghan-born suspect was wanted for questioning in connection with the New York explosion.
His last known address was in Elizabeth, New Jersey, according to the statement.
Earlier on Saturday, a pipe bomb exploded in a trash can in New Jersey on the route of a Marine Corps run before the start of the race, causing no injuries but forcing its cancellation.
There was no claim for the bombings in New York or New Jersey.
In the Midwest, an assailant reported to be a 22-year-old Somali-American college student went on a stabbing spree in a shopping mall in St. Cloud, Minnesota, injuring nine people before being shot dead by an off-duty police officer.
Police confirmed that the assailant asked some victims whether they were Muslim before attacking them.
Amaq news agency claimed that a DAESH "soldier" had carried out the Minnesota stabbings.
A US official involved in the investigation of the explosive devices said that "the crudity of the devices in all three cases certainly doesn't point to any group that's been developing (improvised explosive devices) for years."
The official, who requested anonymity, added that the crude nature of the devices and the apparent low level of planning had some investigators concerned that the blasts were just a test of New York's security.
"That's what worries us: Was this some kind of test run, not just of the devices, but also of the surveillance in New York and the response?" the official said.
"A bomb exploding in New York is obviously an act of terrorism, but it's not linked to international terrorism," Democratic New York Governor Andrew Cuomo said Sunday after touring the scene of the explosion in Chelsea.
"In other words, we find no DAESH connection, et cetera," said Cuomo. But he also stressed the lack of an international terror link was preliminary.