A bomb that injured 29 people Saturday in the Chelsea neighborhood of Manhattan and another that failed to detonate were filled with shrapnel and made with pressure cookers, flip phones and Christmas lights that set off a powerful explosive compound, law enforcement officials said Sunday.
Both bombs appeared designed to create maximum chaos and fatalities. They also provided a trove of clues even as any suspects remained unnervingly at large.
A top law enforcement official said pressure cookers were filled with “fragmentation materials.” The bomb that exploded, at 23rd Street, was filled with small bearings or metal BBs. A second device on 27th Street that did not explode appeared to be filled with the same material, the official said.
Late Sunday, two senior law enforcement officials said they had identified a “person of interest” in the bombing, though they did not refer to that person as a suspect.
Senior law enforcement officials also said that they were increasingly focused on the possibility that the attack was connected to a bombing that took place 11 hours earlier in New Jersey, but the authorities still needed to compare all the bombs before drawing any conclusions. There, three pipe bombs were tied together, placed in a trash can and also employed by a flip cellphone as a timing mechanism, according to officials. Only one of the three pipe bombs detonated, and no one was injured. Officials said the explosive in that device appeared to be black powder.
Officials said they did not know of any motive, political or social, for any of the attacks. Early Sunday, New York Gov. Andrew M. Cuomo said “there is no evidence of an international terrorism connection with this incident,” noting that no international terrorist group has claimed responsibility.
The bombing comes at a time of increasing nervousness around the world after terrorist attacks in Belgium and France, creating a climate where even a false report of gunfire at John F. Kennedy Airport recently triggered widespread panic.
“This is one of the nightmare scenarios,” Cuomo said at a news conference Sunday. “We really were very lucky that there were no fatalities.”
The search for the person or people behind the attack in New York took on added urgency as President Barack Obama and leaders from around the world travel to New York for the annual U.N. General Assembly this week. It was unclear why Cuomo and Mayor Bill de Blasio dismissed with such certainty a tie to international terror.
Experts said the bomb’s construction offered conflicting clues. Tests showed that the explosive material in the 23rd Street bomb was similar to a commercially available compound called Tannerite, according to two law enforcement officials.
It is made by combining ammonium nitrate and aluminum powder, is frequently used in exploding targets at firearms ranges and has rarely been used in improvised explosive devices in the United States. But the materials are easy to buy here because each one on its own is not an explosive.
At the same time, other evidence from the bomb seemed to point overseas. Pressure cookers have been a container of choice for many improvised explosive devices over the years. They were used in the deadly Boston Marathon bombings in 2013 based on a model in publications put out by al-Qaida’s affiliate in Yemen.
An expert on IEDs used by terrorists around the world said that a device constructed with a cellphone as a timer and Christmas lights as an initiator would indicate a higher-than-average competence than is usually found in the United States. “Most of what we in the United States is a pipe bomb with black powder or smokeless powder or a simple hobby fuse,” said the expert, who spoke on the condition of anonymity because he does sensitive work for government agencies. “This would be the high-end of sophistication for IEDs in the United States.”
Cuomo said he was ordering an additional 1,000 New York State Police officers and National Guard members to be dispatched to major commuter hubs, and de Blasio said New Yorkers should expect to see a heightened police presence throughout the city, including additional patrols by the city’s heavily armed counter terrorism units.
The police continued to search the area around the blast site and fanned out across the city chasing leads and trying to sort through a variety of claims of responsibility — from Twitter to websites to 911 calls — most of which they dismissed as unrelated.
Late Sunday, FBI agents were seen tearing apart a car of an Uber driver, who said the law enforcement officials were searching for possible evidence related to the attack.
The bomb was placed under a Dumpster made of heavy-gauge steel, and was powerful enough to catapult the metal box across the street.
The 29 people who were wounded mostly suffered cuts and abrasions and had all been released from the hospital by Sunday morning.
Police Commissioner James O’Neill said the unexploded device was found by two state troopers as they walked down 27th Street after calls to 911 alerted the police to a suspicious device. It was being examined by bomb technicians at a police facility in the Bronx.