Manhattan bomb explosion today at 23rd Street and Sixth Avenue in Chelsea; 29 injured

An explosion rocked the Chelsea neighborhood of Manhattan on Saturday 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.

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.

"It is too early to determine what the incident was caused by. We believe it was intentional. A full investigation is under way."

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.

The bomb in Manhattan happened just hours after a pipe bomb exploded in New Jersey beach.

A pipe bomb exploded in a New Jersey beach town on Saturday along the route of a charity race to benefit military veterans, but no injuries were reported in what investigators were treating as a possible act of terrorism.

The explosive device went off in a trash can about 30 minutes after the scheduled start of the race, which coincidentally was delayed, in Seaside Park, a resort about 80 miles (129 km) south of New York City, officials said.

No damage to surrounding structures was reported, and no runners or bystanders were in close proximity to the 9:30 a.m. blast, so no one was hurt, authorities said.

Even so, the explosion stirred dark memories of the bomb blasts at the finish line of the Boston Marathon in 2013 that killed three people and wounded more than 260 others.

The Federal Bureau of Investigation's so-called joint terrorism task force assumed the lead role in searching for clues to Saturday's bombing, asking members of the public for any tips that might lead to arrests in the case.

The race, dubbed the Seaside Semper Five 5K, was immediately canceled, and authorities closed the beach and several surrounding blocks while evacuating dozens of nearby homes as a search for more devices ensued.

Initial reports of a second bomb planted in another trash proved untrue, according to a statement issued by New Jersey state police several hours later.

Brad Cohen, special agent in charge of the FBI's Newark field office, said at an early evening news conference that investigators had determined there was no longer any threat to the community. Police Chief Francis Larkin said residents forced from their homes were allowed to return.

MATTER OF MINUTES

Authorities said the lag in the start of the race, reportedly because of late registrations, proved fortuitous, as the bomb went off before runners were on the race course.

"It's obvious it was meant to affect the run, the fact that it went off at 9:35," Al Della Fave, a spokesman for the Ocean County Prosecutor's Office, said in an interview on CNN.

The charity run was organized to benefit military veterans and the families of those lost in military service. The run's name is a reference to Semper Fidelis, Latin for "always loyal," the motto of the U.S. Marine Corps.

Asked if Marines and their families had been targeted, Della Fave said, "I think we can assume that, considering the location of the device right along the run route where, if it was just a matter of minutes in terms of difference, there would have been a good number of people running past that explosive device."

The trash can contained several "pipe bomb-type devices" wired together, Della Fave said. "The one went off, and the others did not," he said.

Law enforcement authorities said they did not know the motive for the blast.

The explosive went off near the boardwalk by the intersection of Ocean Avenue and D Street, authorities said. According to a course map for the race, runners would have passed near the intersection twice: once 0.7 miles into the race and again 0.7 miles from the finish.

About 5,000 people were set to run the 5 km race in Seaside Park, a family-oriented resort known for its beachside boardwalk, a local NBC affiliate reported.

At the 2013 Boston Marathon, two brothers of Chechen ethnicity who professed allegiance to Islamist militants planted homemade bombs near the finish line of the renowned race. The subsequent explosions killed and maimed dozens of bystanders in the most high profile attack on U.S. soil since Sept. 11, 2001.