Several St. Pete Beach homes were evacuated and a stretch of beach was cleared Sunday while experts investigated the discovery of a World War II-era flash bomb.

Bomb experts detonated the device around 5:10 p.m. as dozens of curious onlookers watched from a distance. Things quickly returned to normal.

The flash bomb, a cylinder about four feet long with a cone-shaped cap on one side, was found by a walker near the 22nd Avenue beach access around 8:35 a.m.

Pinellas County sheriff's detectives responded to the scene and summoned the Hillsborough County Sheriff's Office bomb squad, which in turn called out the ordnance disposal unit from MacDill Air Force base. Officials said the object had barnacles on it and appears to have been submerged for a long time.

Residents of about 60 homes were notified of the discovery, and about half of those - on the beach side of Sunset Way between 22nd and 28th avenues - were placed under mandatory evacuation.

About 125 people were displaced while the experts decide what to do what the device. Those people were allowed to congregate at a community center, and they're being provided free snacks.

MacDill officials said flash bombs were used by military surveillance aircraft to light up the night sky. Because the devices can still be dangerous, law enforcement personnel built a sand wall around it set up a 300-yard perimeter. A sand wall was also built around a nearby turtle nest.