Investigators have scoured a neighborhood on Manhattan's west side, trying to figure out why a homemade bomb exploded during a busy weekend evening, wounding 29 people.
FBI agents were also examining an unexploded device found four blocks away as well another device that exploded in New Jersey earlier in the day on September 17
The explosion occurred in the Chelsea neighbor, which is home to art galleries, chic eateries, and a large gay population and was teeming with people out on a warm evening.
It sent shudders throughout the city less than a week after the anniversary of the September 11, 2001 attacks.
New York Mayor Bill de Blasio called the blast an "intentional act," and New York State Governor Andrew Cuomo said the initial indications were that it didn't appear to be tied to international terrorism.
"At this time there is no evidence of an international terrorism connection with this incident, but it is very, very early in the investigation and it's just starting," Cuomo told reporters.
WATCH: New York Mayor Says Blast Was 'Intentional Act' (Reuters)
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New York Mayor Says Explosion Was 'Intentional Act'
Most of the injured were treated for minor injuries including shrapnel wounds, although police listed one injury as serious. Cuomo said all had been released from hospital by September 18.
One investigator was quoted by the Associated Press as saying the second device appeared to be a pressure cooker attached to wiring and a cellphone. Such devices were used in the 2013 bombings at the Boston Marathon.
The explosion seemed to have come from a construction toolbox in front of a building, and photos from the scene show a twisted and crumpled black metal box.
The blast happened in front of a residence for the blind, near a major thoroughfare with many restaurants and a supermarket. Witnesses said the explosion at about 8:30 p.m. blew out the windows of businesses and scattered debris.
The pipe bomb that exploded in New Jersey early on September 17 came as thousands of runners were preparing to run in a charity road race benefiting U.S. military personnel. No injuries were reported there and the race was canceled.