As erosion continues to shrink the beach on Folly Island, more and more explosive devices may be exposed, Folly Beach Public Safety Chief Dennis Brown said.

Visitors at Folly Beach County Park found mortar shells along the beach about 2:45 p.m. Tuesday, which prompted authorities to clear the park so the devices could be detonated.

"They found two mortar shells that had been exposed due to the erosion of the beach," Brown said.

The bomb squad from the Charleston County Sheriff's Office was summoned, as was a bomb team from the State Law Enforcement Division, Brown said. Bomb squad technicians told him they thought the devices dated from World War II or earlier, Brown said.

"This used to be an artillery range years ago," he said. "We may see more of these with the continued erosion."

Brown urged anyone who comes across a suspicious device on the beach to refrain from picking it up and to call 911 immediately. He also said people should move away from the device while they wait for authorities to arrive.

"Don't use your cellphone to take a picture of it," he said. Electronic devices can be dangerous around explosives.

For the first few hours, the park was not closed to beach-goers, but authorities kept people away from the devices.

The sheriff's bomb technicians moved the devices from their original locations because the tide was coming in and threatened to cover them up, Brown said. A Charleston Air Force Base ordnance disposal team was summoned, which is standard procedure whenever a device is thought to be a military ordnance.

About 6:30 p.m., authorities asked everyone to leave the park as the devices were prepared for detonation.

Brown said the devices were detonated without incident.