SEASIDE PARK, N.J. — A pipe bomb exploded in a Jersey Shore town Saturday shortly before thousands of runners were due to participate in a charity 5K race to benefit Marines and sailors, authorities said.

No injuries were reported in the blast in Seaside Park around 9:30 a.m. Saturday, said Al Della Fave, spokesman for the Ocean County Prosecutor’s office. He said no surrounding structures suffered any apparent damage, as well.

Investigators would not say if they suspected participants in the third annual Semper Five run were targeted. The race was canceled, and the immediate area was put on lockdown.

The pipe bomb was in a plastic garbage can when it exploded, Della Fave said. Authorities immediately cleared the boardwalk and beach area, and bomb-sniffing dogs were used to search the area.

New Jersey State Police said that bomb technicians “rendered safe” items located in a plastic trash can where the explosion occurred. They also said there was nothing to reports of another explosive device.

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 after an unattended backpack was found, and the area was mostly empty when the bomb went off.