The New York City Police Department (NYPD) leads the investigation by an "intentional" explosion at 8:30 Saturday night in Chelsea, a busy area of Manhattan.
The blast, described as "deafening" by witnesses, wounding 29 people, the Fire Department of New York (FDNY) reported.
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Only one of the victims suffered serious injuries. However, according to FDNY, at noon on Sunday all were discharged from the hospital.
Authorities said at a news conference Sunday that the explosion was "intentional."
According to The New York Times, officials of the security forces said the device used to cause the explosion was a pressure cooker filled with shrapnel connected to a cell phone and some Christmas lights, designed to act as a trigger reported.
Saturday night, authorities found a similar device on 27th Street, a few blocks from the site of the explosion, which failed to be detonated and was removed and destroyed safely.
Both devices are similar to those used in the bombing of the Boston Marathon in 2013.
NYPD announced that it is reviewing the entire area as if it were the scene of a crime and asked the citizens to avoid passing by. However, the authorities have evacuated the area.
Researchers have available area pop videos, originated on 23rd Street near Sixth Avenue. These films together with the explosive device being analyzed, but more information was not provided.
unknown reason
So far the reasons behind the explosion shattered the windows of a nearby building and the windows of a vehicle are unknown.
What is discarded is that it has been caused by a gas leak.
The mayor of New York, Bill de Blasio, said they believe that what happened was the result of a "deliberate act".
He said that so far no evidence that the incident is linked to any terrorist action and said there is currently a credible threat to the city.
However, hours later, on Sunday, the governor of New York, Andrew Cuomo said that although they have found no links with international groups, it is a "terrorist act."
"Those who want to have been the one that has artifacts, find and bring to justice," he added.
1,000 more agents
more than 1,000 agents have been deployed in the city for security tasks especially in the transport network.
The head of Special Operations Police New York, Harry J. Wedin, said the personnel division would review the surrounding buildings to ensure safety in the area.
Also they rushed to the site officials Federal Bureau of Investigation (FBI) and the Department of Homeland Security.
blast in Manhattan came just a few hours after that in a separate incident, a homemade bomb was detonated in a dumpster in New Jersey, near a place that was scheduled to be held a race charity for the war veterans. In that event there were no injuries.
Di Blasio reported so far there is nothing to suggest that the two events are related.
However, officials involved in the investigations told The New York Times that more and more items that make them think about a possible link between the events in New Jersey and New York.
Reaction of candidates
Democratic presidential candidate US, Hillary Clinton, said he was in contact with the authorities in New York.
"We must do everything possible to support the teams of first responder and the victims," he said.
"I will have more to say when we know all the facts."
The Republican candidate Donald Trump also referred to the explosion and did so during a rally in Colorado when he told his followers that a "bomb" had exploded in New York.
"Nobody knows what exactly is going on, but we live in a time ... We better do hard, friends."