Nobody was injured in the blast, which happened at around 9.30am on Saturday morning
A small bomb that exploded along the route of a road race in New Jersey on Saturday morning contained multiple devices that failed to go off, authorities have said.
No one was injured in the blast on Ocean Avenue in the town of Seaside Park, which happened at around 9.30am, shortly before 3,000 runners were due to take part in a charity race to benefit US marines and sailors.
New York City Mayor Bill de Blasio said there was no specific connection between the New Jersey blast and the explosion in Manhattan on Saturday evening that left 29 people injured.
Pictures posted on social media showed a green plastic waste bin blown apart in New Jersey.
Prosecutors said the fact that the charity race was delayed could have prevented large numbers of runners being in the area at the time.
Al Della Fave, spokesman for Ocean County Prosecutor's Office, said the devices in the bin were "wired together" but did not all detonate.
He added that the rubbish bin contained a "pipe bomb-style device", NJ.com reported.
Mr Fave issued a warning on Facebook which said: "At this time the area is on lock down while bomb dogs search for additional devices.
"There is a report of at least one other device which the NJSP will make safe. Please avoid the area."
Officials say the device was timed to detonate during the race but the start was delayed while a suspicious rucksack was investigated.
The race was abandoned after the explosion and nearby houses were evacuated.
Ocean County Prosecutors later said that the investigation was being handled by the FBI.
The incident is likely to evoke memories of the Boston Marathon bombings in 2013 which killed three people injured hundreds more.