New York police have released a picture of a man who is wanted in relation to a recent bomb blasts there, none of which have been deadly.
A bomb detonated in New York, and another device found nearby, were both shrapnel-filled pressure cookers, according to reports.
A bomb detonated in New York, and another device found nearby, were both shrapnel-filled pressure cookers - similar to the bombs used at the 2013 Boston Marathon, reports say.
Citing top law enforcement officials, the New York Times said the two devices were designed to use flip phones and Christmas lights to trigger the explosives.
The blast, in the Chelsea area of Manhattan, injured 29 people, who have all now been released from hospital.
The New York Police Department meanwhile released a picture of Ahmad Khan, who they said was wanted for questioning in relation to the bombings there.
The unexploded second device - reportedly a pressure cooker attached to wiring and a mobile phone - was found four blocks from the site of the explosion, and New York governor Andrew Cuomo said it appeared to be "similar in design" to the exploded device.
Both were different from a pipe bomb that detonated earlier on Saturday on the route of a charity race in New Jersey, Mr Cuomo added. That explosion caused no injuries.
Another blast occurred later in Elizabeth, New Jersey when a robot set off an explosive which was found in a backpack in a train station rubbish bin.
Police refused to give many more details today, although New York Police Commissioner James O'Neill said that "components indicative of an IED" (improvised explosive device) had been found.
Chelsea is among the most fashionable districts of Manhattan and its bars and restaurants are usually crowded at the weekend.
On Tuesday, President Barack Obama and other world leaders are due to attend the UN General Assembly in New York.
Some 1000 extra security personnel are being deployed to New York's transport hubs.
In the Boston Marathon bombing in April 2013, two pressure-cooker bombs packed with shrapnel exploded near the finish line, killing three spectators and injuring about 280.
A police officer was killed during the operation to catch suspects Dzhokhar and Tamerlan Tsarnaev, two brothers believed to be radical Islamists. Tamerlan Tsarnaev died in a shoot-out.
Motive still a mystery
The weekend's bomb attack was a terrorist act, officials say, but no links have been found to global groups and no group has claimed responsibility.
"Was it a political motivation? A personal motivation? We do not know," said the city's mayor, Bill de Blasio.
Mr de Blasio said a lot more work was needed to be able to say what kind of motivation was behind it.
"All possible theories of what's happened here and how it connects will be looked at but we have no specific evidence at this point in time."
Mr Cuomo said: "Whoever placed these bombs - we will find them and they will be brought to justice."
Speaking earlier near the site of the blast, Mr Cuomo said that significant damage had been caused and "we were lucky there were no fatalities".
Mr Cuomo said: "A bomb exploding in New York is obviously an act of terrorism."
"We will not allow these type of people and these type of threats to disrupt our life in New York. This is freedom. This is democracy, and we are not going to allow them to take that from us.
"They want to instil terror. They want to make you worry about going into New York. We're not going to let them instil fear."
Mr Cuomo said that the attack was one of the "nightmare scenarios" a governor must face, but he added: "We have no reason to believe at this time that there is any further immediate threat."
Windows blown out
The Chelsea explosion occurred about 9pm, outside a residence for blind people on West 23rd St.
The force of the blast blew out windows and could be heard several blocks away.
Some reports said the bomb went off in a black metal construction toolbox, others that it was in a rubbish bin.