At least 29 people suffered non-life threatening injuries in an explosion which occurred in a crowded Chelsea neighbourhood in Manhattan on Saturday night. According to the New York Fire Commissioner, Daniel Nigro, one person was seriously injured.
New York Mayor Bill de Blasio said a second site was being investigated.
"Tonight, New York City experienced a very bad incident," de Blasio said at a news conference near the scene. "We have no credible and specific threat at this moment".
A second device was found four blocks away on West 27th Street. According to several local news sources, it was a pressure cooker attached to a mobile phone by tape with protruding wires.
People living on West 27TH Street were instructed to stay away from their windows while the device was investigated. Police, aided by sniffer dogs, combed refuse bins to ensure there were no other devices.
Reacting to the blast, Republican Presidential candidate Donald Trump said: "It is a terrible thing what's going on in our world, what's going on in our country, but we are going to get tough and smart and vigilant and we are going to end it."
The explosion come hours after a pipe bomb went off in Seaside Park, New Jersey, shortly before thousands of runners participated in a charity 5K race to benefit Marines and sailors. The device, which only partially detonated caused no injuries. Authorities are yet to make any connection between the explosion.
Hillary Clinton says she has been briefed about the bombings in New York and New Jersey and the attack in Minnesota.
She says the nation needs to support its first responders and "pray for the victims".
"We have to let this investigation unfold," she said.
In St. Cloud, Minnesota, police said multiple people were injured at a shopping mall Saturday evening in an attack that possibly involved both a shooting and stabbing. The suspect was believed to be dead.
A CCTV camera has emerged online which allegedly captured moment of the Manhattan explosion. See video here: here