At least 29 injured after explosion in New York City’s Chelsea neighborhood

CHELSEA, Manhattan — At least 29 people were injured in an explosion in New York City’s Chelsea neighborhood Saturday night.

New York City Mayor Bill de Blasio says early indications are that the explosion "was an intentional act." But de Blasio says "there is no evidence at this point of a terror connection" and there is no "credible and specific threat" to New York City. The mayor says they also believe this explosion is not connected to the earlier explosion along a race route in New Jersey.

The explosion happened at 135 23rd St. between Sixth and Seventh avenues shortly before 9 p.m.

Gas has been ruled out as the cause of the explosion, a law enforcement source told CNN.

The "exact nature and cause of this explosion has not yet been determined," NYPD Commissioner James O'Neill said during a press conference.

The NYPD Special Operations Division said a possible secondary device has been located. No word on what the second device is. That device was located on 27th Street between Sixth and Seventh avenues.

The area of the explosion is packed with restaurants, subway stations, shops, businesses and art galleries. People living in buildings near the affected area are not being allowed in, CNN's Bernadette Tuazon reported from the scene.

An eyewitness told CNN affiliate NY1 he was having dinner when an explosion rocked the area.

" felt a loud explosion and I felt like a lightning bolt struck the building. It, like, shook the ground," he told NY1. "Everybody ran out of the restaurant into the street. The whole city was in the street."

He says the response by police who swarmed the area was "aggressive" but "controlled."

The man told NY1 he lives in the neighborhood and knows it well.

"I walk down the street every day. ... This is my main thoroughfare. I'm either in an Uber, a cab, or on foot on this street all the time. This is my neighborhood. This isn't a tourist attraction. It's just the middle of the city. It does frighten me."

New York Governor Andrew Cuomo released the following statement on the explosion in the Chelsea neighborhood of New York City.

"State officials are coordinating our response with federal and New York City authorities, and full state resources have been made available for this investigation," Cuomo said. "We are closely monitoring the situation and urge New Yorkers to, as always, remain calm and vigilant."

This is a developing story, check back for updated information.