Pipe Bomb Explodes Along 5K Seaside Park Racecourse on Jersey Shore

The boardwalk area in Seaside Park, New Jersey, was evacuated - and a lockdown was in place - because of an explosion Saturday as authorities continued to search for any possible suspects.

No one was injured in the blast, and no additional devices were found after a search at a charity 5K race that was expected to draw 3,000 people, many of them veterans of the armed services, authorities said.

No one has been arrested in connection with the 9:30 a.m. explosion that involved at least one pipe bomb in a trash can, according to Attorney General Christopher S. Porrino. Authorities say it had no connection to the blast that injured at least 29 people in New York City on Saturday night.

Read update: Pipe Bomb Explosion At Jersey Shore Remains Under Investigation: FBI

The explosion happened just as a Semper Five 5K race event was supposed to begin, according to Porrino. The race had been delayed because of a suspicious backpack that was found in the area.

The race was cancelled. Had the race proceeded as scheduled, authorities say, participants could have been injured by the blast.

“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.”

Residents were allowed back to their homes, but some beaches remained closed during the weekend, and the manhunt for suspects continued.

Read more: Major Jersey Shore Events Cancelled After Seaside Park Pipe Bomb Explosion

Al Della Fave, a spokesman for the Ocean County Prosecutor's Office, said he believes the incident was a deliberate one that might have targeted Marine veterans participating in the event. But he declined to say whether he felt it was a terror attack.

Della Fave said there were multiple bombs wired together - perhaps two or three - but only one exploded.

On the scene were the New Jersey State Police, FBI, U.S. Bureau of Alcohol, Tobacco, Firearms & Explosives, Ocean County Prosecutor’s Office, Ocean County Sheriff’s Department and Seaside Park Police Department.

“Working with the FBI and ATF, we are taking every step to ensure the safety of the public and to determine who was responsible for this explosion, which occurred at a time when runners in this charity race could have been in harms way,” said Porrino.

The FBI has now taken the lead on the investigation.

For several hours, investigators searched for at least one other device in the area, and State Police were conducting a search using bomb dogs, said Della Fave.

No additional explosions or secondary locations were identified, and initial reports of a second device found in another trash can were "refuted," Porrino said.

The Ocean County Prosecutor's Office told people to avoid the area of D Street and Ocean Avenue in Seaside Park after the explosive device discharged in a garbage can.

People in the area were being told to stay inside. "Please avoid the area," Della Fave said.

Traffic into Seaside Park was closed along Ocean Avenue, or Route 35, including Central Avenue between 9th Street and I street. "Access to the beach is not possible today," according to the Ocean County Sheriff's Office.

Here is a map of the area:

Other towns were taking precautions following the explosion. The Festival of the Sea in Point Pleasant Beach was cancelled following the incident.

Read more: Seafood Festival In Point Pleasant Beach Canceled After Seaside Park Explosion

Also, the New York City Police Department said it was closely monitoring the incident, and Belmar took precautions:

Read more: Belmar Ramps Up Police Presence, Inspects Garbage Cans After Seaside Park Bombing Incident: Mayor

Porrino urged anyone with information related to the explosion to call the New Jersey State Police Homeland Security Tipline at 1-866-4SAFENJ.

Race officials in Seaside Park confirmed on Facebook that the race was canceled after the incident.

"Out of extreme precaution, this year's Seaside Semper Five has been canceled due to an unidentified suspicious backpack found at the race site. The safety and security of our participants, spectators, staff and volunteers is of utmost importance."

"We'd like to thank the Seaside Park Police Department, all the first responders and emergency personnel for their quick action. Further details will be posted when available. Thank you for your understanding."

This was to be the third year of the Semper Five race, which raises funds for the MARSOC Foundation. The foundation assists Marines who are members of the Special Operations Command and their families.

Members of MARSOC “are away from home and family more than 50 percent of the time, either on deployment or out-of-area training. During their service to our country, they are often exposed to combat and other hazardous activities that can have immediate and lasting impacts,” the foundation notes.

“The foundation aims to meet needs unmet by the government with an emphasis on building personal and family resiliency and supporting the full reintegration of MARSOC Marines and Sailors following wounds, injuries and extended deployment.”

The race kicks off with a run by active-duty Marines at the U.S. Embassy in Afghanistan, then is completed in Seaside Park. The race was scheduled to start and end at The Sawmill restaurant, organizers said.

While many people are familiar with boisterous Seaside Heights thanks to MTV's "Jersey Shore" show, Seaside Park is its quiet neighbor to the south. The borough encompasses just three-quarters of a square mile and is home to 2,200 year-round residents and dozens of summer homes, according to the borough's website.

Seaside Park sits between Seaside Heights and the South Seaside Park section of Berkeley Township, both of which lead to Island Beach State Park and are a pass-through for many headed to the state park's quiet beaches and renowned surf fishing.

Here is a 911 recording of dispatch communications regarding the attack:

Here is News12 coverage of the incident as it happened:

By TOM DAVIS and KAREN WALL

Photo: Ocean County Prosecutor's Office