UPDATED 1:41 a.m. 9/18/16
NEW YORK (CBSNewYork/AP) -- Mayor Bill de Blasio said authorities believe an explosion in Chelsea that left more than two dozen people hurt was "an intentional act" as police investigate a possible secondary device a few blocks from the scene.
Sources told CBS2 that the possible second device found on West 27th Street between Sixth and Seventh Avenues is a pressure cooker with a cell phone and wires attached found in a plastic bag.
The exact cause of the blast on West 23rd Street, which happened at about 8:30 p.m. Saturday, has not been determined, but officials said they don't believe natural gas was responsible.
"Tonight, New York City experienced a very bad incident,'' de Blasio said at a news conference near the scene. "We have no credible and specific threat at this moment."
De Blasio also said there was no evidence yet that the explosion was connected to terrorism.
"I want to assure all New Yorkers that the NYPD and all other agencies are at full alert, and that our anti-terror capacity in particular is at full alert," de Blasio said at a late night news conference.
Fire Commissioner Daniel Nigro said a total of 29 people were injured in the blast. He said one person's injuries were serious and the rest were minor.
Bellevue Hospital Center reported it treated nine patients, none of whom had life-threatening injuries.
Police Commissioner James O'Neill said officers are investigating a possible second explosive device a few blocks away from the explosion on 27th Street between Sixth and Seventh Avenues.
Police sources told CBS2 the second device was a pressure cooker with a cellphone and wires attached, and was found in a plastic bag.
The second device did not detonate. The NYPD Bomb Squad was working to contain and disarm the device, sources said.
It was not clear if the second device was viable or had explosive capabilities, sources said.
City Councilman Cory Johnson said the area of the blast would have been busy on a Saturday night. Witnesses said the explosion blew out the windows of businesses in the area.
"This is a very dense area, the whole block is restaurants and residences and this area on a warm Saturday night is an area swarming with people," Johnson told 1010 WINS.
Roselyn Olivares, who lives on 23rd Street between Sixth and Seventh avenues, said the blast did damage to her fourth floor apartment.
"My bedroom window was blown out," she told 1010 WINS. "We didn't know what it was."
The White House said President Barack Obama has been briefed of the explosion and will be updated as additional information becomes available.
The MTA says 1 and 2 subway trains are not running between Chambers and 34th Street due to the police activity on 23rd Street.
Officials say drivers should also expect extensive traffic delays and street closures in the area. Early Sunday, authorities said all crosstown traffic headed east and west is closed from 14th Street to 32nd Street between Fifth and Eighth avenues. The closures are in effect until further notice.
For current traffic information, click here.
The blast came hours after a device exploded in Seaside Park, New Jersey Saturday morning, shortly before thousands of runners participated in a charity 5K race to benefit Marines and sailors.
De Blasio said at this point, there is no indication that the two incidents are connected.
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