SEASIDE PARK, N.J. (CBSNewYork/AP) — The FBI has taken over the investigation into a blast in Seaside Park that occurred shortly before thousands of runners were due to participate in a charity 5K race to benefit Marines and sailors.

Brad Cohen, the acting special agent in charge of the FBI’s office in Newark, declined to discuss the matter at length during a brief news conference staged Saturday evening.

He said the FBI is working side by side with federal, state and local officials to find out who is behind the device.

“We’re out there conducting interviews, we’re out there securing evidence and we’re making sure that there is no stone left unturned,” Cohen said at a news conference Saturday evening.

But officials won’t say whether they believe the incident was terror related. Cohen declined to take questions from reporters, citing the “active, ongoing” investigation.

No injuries were reported in the blast, which happened around 9:30 a.m. Saturday, when a device exploded inside a plastic garbage can at the corner of D Street and Ocean Avenue, authorities said.

“I heard this big bang go off and they’re putting a modular house up on the next street with this huge crane and I thought they dropped one of them because the house literally shook,” Barbara Williams, who lives nearby, told 1010 WINS’ Samantha Liebman.

Authorities immediately cleared the boardwalk and beach area and bomb-sniffing dogs were used to search the area.

“Right now, looking at it, it’s just a hole in the bottom of the trash pail,” Ocean County Prosecutor’s Office spokesman Al Della Fave said. “Which would indicate that hopefully, the blast would not have been that traumatic or that significant.”

Della Fave told reporters at the scene that preliminary reports said there may have been other devices inside the garbage can, but those devices apparently had not gone off.

“When one went off, there were additional devices in the same pail that did not go off,” he said. “This would have been a device, especially since there were multiple other devices wired to the one that did go off in the same can, and obviously it was to do damage and cause injury.”

New Jersey State Police said later in the day that bomb technicians “rendered safe” items located in the plastic trash can where the explosion occurred. They did not specify what those items were or provide further details, citing the ongoing investigation. They also said there was nothing to reports of another explosive device near the site of the explosion.

Investigators would not say if they suspected participants in the third annual Semper Five run were targeted. Officials said runners had been scheduled to pass by the area around the time the blast occurred.

But the start of the race had been delayed, apparently due to the large numbers of people registering for the race and reports of an unattended backpack being found. The area was mostly empty when the device went off.

Della Fave said if not for the delay, “there could have been great harm.”

Following the blast, the race was canceled and the immediate area was put on lockdown.

It wasn’t clear when the boardwalk and beach would reopen. Some homes near the scene were evacuated as a precaution, and the public was being urged to avoid the area.

Chief of Police Francis Larkin said residents were being allowed to return back to their homes Saturday evening. He said residents living in the areas of C, D and E streets where the investigation is underway will have to show identification to officers to access their homes.

Other community events went on as planned in nearby towns on Saturday, though officials said security at those sites had been stepped up in the wake of the blast.

Attorney General Christopher Porrino and Col. Rick Fuentes, superintendent of the state police, briefed Gov. Chris Christie on the investigation.

“We are grateful that nobody was injured, but this is a serious act of violence against the people of New Jersey,” Porrino said. “We will not rest until we find the person or persons responsible.”

On its Facebook page, organizers for the race said that “the safety and security of our participants, spectators, staff and volunteers is of utmost importance.”

They also thanked police and other first responders “for their quick action.”

The NYPD said it was closely monitoring the investigation.

Anyone with information related to the explosion is being asked to call the New Jersey State Police Homeland Security Tipline at 1-866-4SAFENJ.

If anyone has information regarding #Seaside Park incident please call 1-800-CALLFBI Option 1 #FBI #FBINewark — FBI Newark (@FBINewark) September 17, 2016

You can also call the FBI at 1-800-CALLFBI Option 1.

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