New York's Governor Andrew Cuomo says the bombing that wounded 29 people does not have any links to "international terrorism".
The explosion tore through Chelsea, a residential district of Manhattan that is popular for its nightlife, late on Saturday. Police later discovered a second bomb four blocks away, that was safely defused and taken away for analysis.
"A bomb exploding in New York is obviously an act of terrorism, but it's not linked to international terrorism. In other words, we find no ISIS connection, etc," said Cuomo in reference to the Islamic State of Iraq and the Levant, also known as ISIL.
Mayor says New York blast was carried out deliberately
Late on Sunday night, ABC News and a New York senator said FBI agents took five men into custody in connection with the explosion. But the FBI quickly said that no arrests had been made and that earlier news reports were incorrect.
"We conducted a traffic stop of a vehicle of interest in New York City but no arrests were made and no one has been charged with any crime," FBI spokeswoman Kelly Langmesser told Reuters news agency by telephone.
She said the investigation was continuing.
Earlier on Sunday, New York's Mayor Bill de Blasio told a news conference: "There is no specific and credible threat against New York City at this point in time from any terror organisation."
De Blasio said that, though injuries were significant, none of those hurt was likely to die.
"It is too early to determine what the incident was caused by. We believe it was intentional. A full investigation is under way," the mayor said.
A police official said on Twitter a second device was being investigated.
Al Jazeera's John Terrett, reporting from New York, said police had "found some kind of pressure cooker … wrapped in silver duct tape. It has wires protruding from the centre of it, and on the side of it is some kind of device thought to either be a timer or a cellphone".
A bomb disposal team was on the scene on Sunday morning and alert notifications were sent out to mobile phones across Manhattan, cautioning those in the vicinity of 27th Street "to move away from the windows", said Terret.
The disposal unit later removed the device from Manhattan for analysis at a specialised facility.
Terrett said police had ruled out gas or faulty construction equipment being the cause of the blast.
"They're saying it's not linked to terrorism at the moment, but that doesn't mean that it isn't," Terrett said. "It means that they have no evidence and that the investigation continues."
Police combing the area around the scene of an explosion found a pressure cooker nearby connected to a cell phone [EPA]
Source: Al Jazeera News And Agencies