NEW YORK — An explosion rocked a crowded Manhattan neighborhood and injured 29 people, and a suspicious device discovered blocks away was safely removed early Sunday.

In a Sunday morning news conference, New York Governor Andrew Cuomo said the incident was terrorism, although there was no evidence that it was international terrorism.

"Tonight, New York City experienced a very bad incident," Mayor Bill de Blasio said. "We have no credible and specific threat at this moment."

De Blasio tried to calm any fears among nervous New Yorkers, saying preliminary information found "there is no evidence at this point of a terror connection" and the explosion wasn't related to a pipe bomb explosion earlier Saturday in New Jersey that forced the cancellation of a charity run.

"Now, I want to be clear: Whatever the cause, whatever the intention here, New Yorkers will not be intimidated," the Democratic mayor said. "We are not going to let anyone change who we are or how we go about our lives."

The explosion happened in Chelsea, a primarily residential neighborhood on Manhattan's west side that's known for its art galleries and large gay population.

It was unclear who was behind the blast and what motivated it.

A law enforcement official told The Associated Press that a second device that officers investigated four blocks from the scene appeared to be a pressure cooker attached to wiring and a cellphone. The official, who was not authorized to speak about an ongoing investigation and spoke on condition of anonymity, said the device was found inside a plastic bag on West 27th Street. The device was removed with a robot and taken to a department firing range in the Bronx.

The law enforcement official also said that the explosion that rocked a bustling Chelsea neighborhood appeared to have come from a construction toolbox in front of a building. Photos from the scene show a twisted and crumpled black metal box.

The blast happened on West 23rd Street, in front of a residence for the blind, near a major thoroughfare with many restaurants and a Trader Joe's supermarket. Witnesses said the explosion at about 8:30 p.m. blew out the windows of businesses and scattered debris.

The Fire Department of New York said 29 people were injured, and 24 people were taken to hospitals. One person received a puncture wound that was considered serious. The other injuries were described as scrapes and bruises.

New York City subway routes were affected by the explosion, which rattled some New Yorkers and visitors on the heels of the 15th anniversary of the 9/11 terror attacks.