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.
Read more: BBC News