A powerful explosion caused by what the authorities believe was a homemade bomb injured at least 29 people on a crowded sidewalk in the bustling Chelsea neighborhood of Manhattan on Saturday night, according to the police.
A few hours later, the authorities found and removed what they described as a second explosive device four blocks away, raising the possibility that two bombs had been planted in the heart of the city.
Police officers swarmed Chelsea’s streets after the blast, which reverberated across a city scarred by terrorism and vigilant about threats, just days after the 15th anniversary of the Sept. 11 attacks.
As the authorities sought to identify what had caused the explosion, they described the second device as a pressure cooker resembling the one used in the deadly Boston Marathon bombings in 2013, according to a police official, who spoke on the condition of anonymity to discuss a continuing investigation.
It was unclear whether the blast on West 23rd Street had been caused by the same type of explosive.
In the immediate aftermath, the police shut down a swath of Manhattan south of Midtown. The area from 14th Street to 32nd Street was closed to traffic between Fifth and Eighth Avenues. But by 7 a.m., only 23rd Street remained closed.
A grim New York City Mayor Bill de Blasio, speaking at a news conference at the scene around 11:15 p.m., said “injuries are significant.” But for the moment, he said, none of them were life-threatening.
Many of the injuries were caused by shrapnel from the explosion, which witnesses said seemed to have started inside a sidewalk Dumpster near the Avenue of the Americas.
The impact shattered windows, damaged cars and sent crowds running from the scene at an hour when Chelsea, always a popular destination, was filled with residents and tourists.
The blast occurred outside the Associated Blind Housing facility at 135 W. 23rd Street. Mayor de Blasio has said that the explosion appears to be a deliberate act. “Early indications are that this was an intentional act,” he said, adding that the area is being treated as a crime scene.
De Blasio specified there was no threat of a bigger attack in the City. “There is no specific and credible threat against New York City at this point in time from any terror organization.” However, the possibility of the explosion being a terror attack has not been ruled out yet. “Whatever the cause,” Mr. de Blasio said, “New Yorkers will not be intimidated.”
According to the New York City Fire Commissioner Daniel Nigro, 29 people were injured in the blast, with one person reported to have sustained grievous injuries.