An explosion rocked the Chelsea neighborhood of Manhattan on Saturday (September 17) night, injuring at least 29 people, authorities said, adding that they are investigating the blast as a criminal act not immediately linked to any terror organization.

Mayor Bill de Blasio said early indications were that blast was intentional. He said the site of the explosion, outside on a major thoroughfare of a fashionable enclave in one of the most bustling areas of New York City, was being treated as a crime scene.

"We believe at this point in time this was an intentional act," said de Blasio.

But he said there was no evidence of a "credible and specific threat" to the city. "We do not see a link to terrorism," he added.

The city's Fire Commissioner Daniel Nigro described the injuries the blast caused.

"There are 29 injuries here, one considered serious. 24 of these people have been transported to are hospitals with various degrees of scrapes, abrasions, from glass, from metal. Thankfully none of these are life-threatening injuries," said Nigro.

A law enforcement source said an initial investigation suggested the explosion occurred in a dumpster but the cause was still undetermined. The head of the New York Police Department's special operations division said on Twitter that a "possible secondary device has been located" in the same general area.

CNN reported that law enforcement sources believe an improvised explosive device caused the blast.

A blast in New York City's Chelsea neighborhood on Saturday night caused 29 injuries with none of them life threatening, the city's Fire Commissioner Daniel Nigro said at a news conference.