The investigation into an explosion on Saturday in an upper-class Manhattan neighbourhood is "definitely leading" in the direction of "terrorism", New York City Mayor Bill de Blasio said.
The announcement came as the New York Police Department said authorities were searching for 28-year-old Ahmad Khan Rahami in connection with the bombing. He is a New Jersey resident and a naturalised citizen from Afghanistan.
The NYPD released Rahami's photo on Monday, and the Mayor de Blasio said he could be "armed and dangerous".
In a statement on Monday, New York Governor Andrew Cuomo said that the investigation "suggests [the explosion] may be foreign related, but we'll see where it goes".
On Sunday, Cuomo had effectively ruled out a link to international terrorism, saying there was no evidence to suggest it.
The bomb went off on Saturday in Manhattan's Chelsea neighborhood, injuring 29 people. All of the injured have since been released from the hospital.
A homeland security official told Reuters news agency on Monday that the five devices found in New Jersey early on Sunday night were connected to Saturday's blast in Manhattan.
Five explosive devices were found in a backpack near a New Jersey train station on Sunday night. One of the five devices exploded early on Monday morning as authorities worked to disarm it.
Al Jazeera's Tom Ackerman, reporting from one of the stalled trains in nearby Metuchen, New Jersey, said that authorities had "suspended all services on trains south and west of New York City because of reports of a possible live bomb had been found in a trash can at the Elizabeth station".
Governor Cuomo told national broadcaster MSNBC that authorities had no information suggesting further attacks, but that people should be ready.
Source: Al Jazeera News And Agencies