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NEW YORK — Gov. Andrew Cuomo announced Sunday that 1,000 additional New York State Police officers and National Guard troops will be deployed across New York City following an explosion in Chelsea.

The stepped-up security is “just to err on the side of caution,” Cuomo said. “I want New Yorkers to be confident when they go back to work on Monday that New York is up and running and we’re doing everything that we need to do.”

As the United Nations prepares to host world leaders arriving for the General Assembly, a spokesman told The Associated Press that the organization is assessing security.

U.N. Spokesman Stephane Dujarric said Sunday that security inside the complex “is being assessed on a constant basis.”

He pointed out that security outside the U.N. is the responsibility of the host country.

“We receive great cooperation and appreciate the support from the federal authorities and the NYPD throughout the year, and especially during the General Assembly to keep staff, delegates and visitors safe,” Dujarric said.

Investigators found components “indicative of an improvised explosive device (IED)” at the initial Chelsea blast site Saturday night, leading Police Commissioner James O’Neill to say “we definitely had a bombing.”

Authorities still don’t know who had placed the device or what was the motivation behind the explosion at West 23rd Street that had injured 29 people.

MTA and PATH train service has been restored and both systems suffered no structural damage. All trains running on the E, F lines will continue to bypass 23rd street station and trains running on the No. 1 line will not stop at 23rd or 28th street stations.

“Protecting the safety of New Yorkers and our state’s visitors is priority number one,” Governor Cuomo said. “After thorough inspection, train service has been restored and we continue to work closely with our local and federal partners to monitor the situation. Out of an abundance of caution, we are increasing security at high-profile locations across the city, and all state agencies continue to remain on alert.”

Metropolitan Transportation Authority

The MTA has increased its patrols and surveillance in order to provide heightened protection across all its agencies. The MTA Police Department has stepped up its uniformed and plainclothes presence, and police canine teams and emergency service units will provide extra protection as well as a noticeable sign of increased security. Railroad customers will also see surge patrols, increased step-on/step-off patrols of trains, and random bag checks at various locations.

PATH

As previously announced, PATH service to 23rd Street and 6th Avenue has been suspended for the weekend to allow work to continue on the tunnels. Work crews were in the uptown tunnel on Saturday evening, and the tunnels have been determined safe for passenger service at this time. PATH service to 23rd Street will resume at 5 a.m. on Monday. The Port Authority Police Department has increased high-visibility patrols at all Port Authority facilities.

New Yorkers are reminded to stay alert to their surroundings, and to report any suspicious activity.

Reports can be made to the Counter Terrorism Center at the New York State Intelligence Center via its terrorism tip line: 1-866-SAFENYS (1-866-723-3697); or by email: ctcenter@nysic.ny.gov.

The Associated Press contributed to this report.