NEW YORK, NY — A street-corner explosion that law enforcement sources said was caused by an intentionally detonated improvised device in the busy Chelsea neighborhood of Manhattan sent shrapnel flying into pedestrians Saturday night, injuring at least 29 people, including one person believed to be in serious condition. The blast shattered windows, shook buildings, closed subways and blocked buses from their routes.

Police and other emergency workers responded to the scene at 23rd Street and Sixth Avenue at about 8:30 p.m. Dozens of police officers, firefighters and medical technicians quickly carted the wounded into ambulances and ferried them to nearby hospitals.

The explosion happened on the street outside of 131 W. 23rd St., a hotel, The Townhouse Inn of Chelsea and residential assisted living center for the blind, Visions at Selis Manor, police said.

“Early indications are this was an intentional act,” Mayor Bill de Blasio said at a press conference late Saturday at 23rd Street near Fifth Avenue — about two blocks from the explosion. At the same time he added “there is no evidence of a terror connection, there have been no credible threats against New York City from terrorist organizations.”

Police are scheduled to hold a briefing at noon on Sunday to further update the investigation into the explosion.

Chief Harry Wedin, head of the New York Police Department’s Special Operations Division, said investigators found a “possible” second device on 27th Street between Sixth and Seventh avenues. That device was safely removed by police at about 2:30 a.m. Sources said the device was taken to the NYPD facility on Rodman’s Neck in the Bronx.

Sources said the device on 27th Street was found in a vehicle and it appeared to be a pressure cooker rigged to explode similar to the devices used in the Boston Marathon bombings. The device had wires protruding and what appeared to to be a cell phone taped to it.

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