NEW YORK (NBC News/Jonathan Dienst, Tom Winter, Richard Esposito, Emmanuelle Saliba, Phil Helsel and Elisha Fieldstadt) — An explosion that rocked a crowded Manhattan neighborhood Saturday night and injured 29 people has been determined to be an "intentional act," and Gov. Andrew Cuomo said it was clearly "an act of terrorism."
The explosion, on West 23rd Street between Sixth and Seventh Avenues in the Chelsea neighborhood, was reported at around 8:30 p.m. Twenty-nine people were hospitalized with injuries, but they had all been released by Sunday afternoon, authorities said.
"A bomb exploding in New York is obviously an act of terrorism," Cuomo said Sunday morning.
Less than three hours after the blast, an object police described as a "possible secondary device" was found just a few blocks away from the original explosion while officers were combing the area. Cuomo said the device was "similar in design" to the one that detonated just blocks away.
It was later sent to an NYPD range in the Bronx aboard a special containment vessel, the New York City Mayor Bill de Blasio's office said.
De Blasio said Saturday night that the blast had not been linked to terror, but Cuomo clarified that the explosion had not been linked to an international terror group. "A bomb going off is generically a terrorist activity," Cuomo said.
On Sunday afternoon, De Blasio and other city officials stressed that the investigation was in early stages and while investigators could determine the blast was "criminal" and "intentional," they hadn't nailed down a suspect or a motive.
No arrests have been made, but NYPD Commissioner James O'Neill said "New York City residents can rest assured that we'll get to the bottom of this."
Still, O'Neill, who was sworn in just a day before the blast, said the situation had him worried. "We did have a bomb detonated on 23rd street and we have no one apprehended so of course I'm concerned."
Again, we urge and remind everyone, if you have any information on the Chelsea explosion share it by calling #800577TIPS— NYPD NEWS (@NYPDnews) September 18, 2016
Security had already been tightened in the city for the ongoing United Nations General Assembly, but the presence of officers throughout New York City after the blast would be "bigger than ever," De Blasio said.
Cuomo ordered 1,000 New York State police and National Guardsmen across the city.
Police had said the blast in the Chelsea neighborhood of Manhattan appeared to come from inside a large trash bin, and law enforcement sources said they have video of a man dropping something into or next to a dumpster.
Videos like that — from nearby businesses —are what detectives want to get their hands on from both 23rd and 27th streets to see who was there before the explosions, said NYPD Chief Carlos Gomez.
He said the investigation would take time. "There's a lot of people out on the street on a warm Saturday evening in Manhattan," he said.
New Yorkers were encouraged to remain vigilant Sunday, and call police with any information they may have about either device.
The explosion sent a dumpster flying more than 150 feet down the sidewalk and shattered windows more than a block away, said a senior law enforcement official.
After viewing the extensive destruction, Cuomo said it was "fortunate" no one had been killed. "When you see the damage, it's amazing that no one was killed to tell you the truth. We're lucky that only 29 were injured," Cuomo said on MSNBC Sunday.
President Barack Obama was apprised of the situation, a White House official said.
"The initial indication is this was an intentional act," de Blasio told reporters at the Saturday night press conference.
There was also "no specific and credible threat against New York City at this point in time from any terror organization," the mayor added.
Cuomo reiterated Sunday morning that there was no further credible threat, and urged New Yorkers to "err on the side of caution" but feel comfortable to go about their daily business.
"We will not allow these type of people and these type of threats to disrupt our life in New York. That's what they want to do and we're not going to let them do it," Cuomo said.
"They want to make you worry about going into New York City or New York State. We're not going to let them instill fear because then they would win," he added.
"Bottom line on this is ... whoever placed these bombs we will find and they will be brought to justice," Cuomo said. "Period."
The FBI Joint Terrorism Task Force was on the scene. The federal Bureau of Alcohol, Tobacco and Firearms said a New York arson and explosives task force had responded to the blast.
The "possible secondary device" was found at 27th Street between Sixth and Seventh Avenues, the New York Police Department said on Twitter shortly after 11 p.m. ET.
Three law enforcement sources told NBC News investigators at the second location were examining what appeared to be a pressure cooker with "tape, wires and a cell phone" left on the sidewalk. The bomb squad was investigating although it had not been confirmed that the object was an explosive device.
Huge explosion in Chelsea blew this dumpster ... pic.twitter.com/1lSIGjRyC8— Chris Duffy (@voicehalf) September 18, 2016
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