New York officials are looking for a naturalised US citizen who was born in Afghanistan for questioning over Saturday’s blast in the Chelsea area in which 29 people were injured.
The suspect has been named as Ahmad Khan Rahami, aged 28.
Early on Monday, a backpack containing up to five devices exploded in Elizabeth, New Jersey, when a bomb disposal robot tried to deactivate it.
The suspect’s last known address was in Elizabeth.
FBI officials were searching a residence in the New Jersey city on Monday.
Investigators have warned that the suspect should be considered “armed and dangerous”.
“Anyone who sees this individual or knows anything about him or his whereabouts needs to call it in right away,” New York Mayor Bill de Blasio said on CNN.
Both the bomb that went off in New York on Saturday and an unexploded device found nearby were shrapnel-filled pressure cookers, according to US media.
New York Governor Andrew Cuomo said on Monday that there might be a foreign connection to the Manhattan attack. Officials had said over the weekend there were no confirmed links to international terrorist groups.
The backpack in New Jersey was found near the railway station in Elizabeth.
It was picked out of a bin by two men on Sunday evening, who thought the bag could contain something of value.
“That was not a controlled explosion,” said Elizabeth Mayor Christian Bollwage, adding that the blast, in the early hours of Monday morning, happened as a robot examining a device cut a wire. No one was injured.
Authorities are still working to establish whether the multiple explosive devices found over the past few days are connected.