Law enforcement officials are on the hunt for whoever is responsible for Saturday night's explosion in Chelsea — and sources say a "person of interest" appears in surveillance video taken near the location where a second unexploded device was found.

At least 29 people were injured in the blast, one seriously, when the explosion occurred on West 23rd Street between Sixth and Seventh avenues at around 8:30 Saturday night.

Meanwhile the Associated Press reported Sunday night that authorities had pulled over a "vehicle of interest" in connection with the explosion and were questioning its five occupants.  However an FBI spokesperson told the AP that no charges had been filed.  

Mayor de Blasio called the explosion "a deliberate act," but so far there are no links to terrorism — a position he reinforced Sunday at a press briefing. 

"The early indications is that this was an intentional act," the mayor said. "We're going to have a lot more to say in the coming hours but we believe at this point in time that this was an intentional act. I want to assure all New Yorkers that the NYPD and all other agencies are at full alert."

At a media briefing at police headquarters Sunday, de Blasio said there will be a large police presence around the city.

"We know from everything we've seen so far that this was an intentional act," the mayor said Sunday. "I want to reaffirm what I said last night. But again, we do not know the motivation, we do not know the nature of it. That's what we have to figure out."

Governor Andrew Cuomo toured the area Sunday morning. He said all 29 people injured have been released from the hospital, adding that based on the damage he saw we are lucky no one was killed.

Transit officials said the blast did not damage subway structure at the 23rd Street station.

Cuomo said New York City subway and New Jersey Transit stations in the area could be open in time for Monday morning rush hour.

"The MTA is ready to be up and running as early as tomorrow to return to full service for those stations," he said Sunday at the site of the explosion.

On Sunday night, the MTA announced restored service on 1 trains which had been bypassing both 23rd and 28th streets. E and F trains are still bypassing 23rd Street.

Several roads are still blocked off to vehicular traffic as authorities continue to investigate.

Cuomo met with MTA officials and toured subway stations in the area Sunday morning.

The governor also said the state will be deploying close to 1,000 additional police and national guard officers to police transit hubs and airports.

Witnesses tell us fragments were sent flying when the blast went off.

Video surfaced on social media of the explosion going off on the street, sending people running.

Police say they also found a suspicious device just four blocks away on West 27th Street between Sixth and Seventh avenues. Police say that device was rendered "safe" at an NYPD facility in the Bronx and taken to Virginia for FBI analysis.

The mayor has asked for patience while the investigation continues, and is encouraging New Yorkers to remain vigilant, while cautioning against the impulse to jump to conclusions.

"This was a very serious incident," the mayor said. "It's going to take a lot of careful investigation to get to the facts and to get to the truth. And one of the things we're going to say to you is today is we're going to very careful and patient to get to the full truth here. We are not gonna jump to conclusions, we're not going to offer you easy answers. We're going to make sure we have all the facts.