Counter-terrorism officials were on Sunday searching for a bomber at large after 29 people were injured by a roadside blast in New York and a suspected unexploded second bomb was found nearby by police.
Investigators were examining a device inside a pressure cooker, apparently wired to a mobile phone, which was discovered inside a plastic bag a few blocks from where a powerful explosion fired shrapnel at pedestrians on Saturday night.
“Whoever placed these bombs, we will find and they will be brought to justice,” New York governor Andrew Cuomo told reporters at the scene. “We will not allow these kinds of people and these kinds of threats to disrupt our life in New York.”
No one has claimed responsibility for the attack, according to authorities. “We do not know the motivation,” New York mayor Bill de Blasio said at a press conference at NYPD headquarters.
All those hospitalised by the blast were said to have been released by late on Sunday morning. Significant damage to surrounding buildings was reported, with windows being smashed as passersby screamed and ran for cover.
“When you see the damage, I think we were fortunate that there were no fatalities,” Cuomo said.
The explosion and second device were being investigated by the NYPD, New York state police, the FBI and a joint terrorism taskforce made up of officials from dozens of different local and national agencies. The governor and other officials said no evidence had been found linking the bombs to major international terrorist groups. Such an intentional explosion in a public place was, however, “generically a terrorist activity”, Cuomo said.
CCTV video footage from around the two sites was being pored over for potential leads. The discovery of the still-intact pressure cooker and mobile phone offered the prospect that the purchase of the items may be traceable, leading investigators to a possible culprit or culprits.
Bill Sweeney, a senior FBI agent in New York, said at the press conference alongside de Blasio that authorities would not be disclosing details of the inquiry’s initial findings so as not to “inform the subjects”.Investigators said they were also examining an online posting from someone claiming to be “the NY bomber”. It was not clear if the posting was genuine.
ABC News reported that investigators believed the exploded bomb had been made from Tannerite, a powdered substance designed to make exploding targets for shooting practices that is easily bought online.
About 1,000 additional state police officers and national guard officials will be deployed to monitor New York’s transport system and other important sites, Cuomo said, to ensure that “New York is up and running” for the working week.
The bombing occurred as New York prepared for the opening of the United Nations general assembly on Monday. The annual conference draws thousands of foreign leaders and diplomats to Manhattan, creating complicated security demands.
The explosion rang out soon after 8.30pm Saturday, on West 23rd Street between 6th and 7th avenues in the Chelsea section of Manhattan. The area, which mixes residential properties, shops and restaurants, was bustling with people enjoying a warm evening.
Officials told reporters the bomb appeared to have exploded either inside or beside a construction dumpster on the street outside a small hotel and a facility for blind people.
The pressure cooker was discovered about three hours after the first explosion, four blocks to the north, by officers seeking potential secondary bombs. The device drew comparisons to pressure cooker bombs that exploded amid crowds at the 2013 Boston Marathon, killing three people and wounding dozens of others.
Directions for how to build pressure cooker bombs in a home kitchen notoriously featured in the first issue of Inspire, an English-language online magazine affiliated with al-Qaida.
The first device in New York exploded on Saturday just hours after a pipe bomb blast in neighbouring New Jersey shortly before thousands of runners were due to take part in a charity 5km race for the benefit of US Marines and sailors.
The explosion tore through a plastic garbage can in the borough of Seaside Park at about 9.30am, according to authorities. No injuries were reported and no surrounding buildings appeared to be damaged.
“They are terrorism, though, there’s no doubt about that,” Christie told CNN. “They’re terrorism – who is responsible is something else, and what the motive was is something else that hopefully we’re going to find out.”Governor Chris Christie of New Jersey said on Sunday that no evidence had yet been found linking the pipe bomb in his state with the later explosions in New York. Cuomo said: “The bombs that were in Seaside, New Jersey, appear to be different than the ones in Manhattan.”
Also on Saturday, eight people were stabbed by a man at a shopping mall in Minnesota. Responsibility for the non-fatal stabbings were claimed online by supporters of the self-styled Islamic State.
One witness to the New York explosion, Deborah Griffith, told the Guardian she had seen the blast “like a volcano”.
People were running everywhere, she said, and “it was real loud”. The explosion was red in the centre, she said, producing a wall of flame. Griffin thought it was a gas explosion: she was shopping at Home Depot and was seven doors away when the blast happened.
“The explosion was so big,” she said. “People were running for their lives.”
Another witness, Soleil Philomena, a Chelsea resident, said she had just stopped at a grocery store to buy a magazine.
“I came back out,” she said, “and I heard ‘boom!’ I thought it was fireworks, but everything was shaking, the buildings, my body was shaking. I looked up there was a big cloud of smoke. I saw smoke, it was like a mushroom cloud of black smoke.
“People started running past me and I started running with them. Then we were hugging each other, everyone was so shocked.”