An Air Force bomb squad detonated a barnacle-covered explosive from World War II that had washed ashore on the beach in St. Pete, Florida. The 4-foot cylindrical bomb was spotted by a beachgoer who alerted officials Sunday morning, according to reports.

Sgt. Ali Rose of MacDill Air Force Base confirmed the military ordnance to be a M122 photoflash bomb. According to USA Today, officials said the bomb "appeared to have been submerged for a significant period."

Authorities of the Pinellas County Sheriff's Office, Florida, and MacDill Air Force Base, reportedly evacuated about 250 beachgoers and about 25 homes before blowing up the bomb. They built a 900-foot safety boundary around the explosive device and further expanded it to about 1,400 feet before safely detonating it around 5 p.m., the Associated Press reported.

According to the Massachusetts Institute of Technology, photoflash bombs were dropped by military aircraft and detonated in the air to produce light for photographs, according to a description on MIT’s website. The advent of satellite imagery and better nighttime optics eventually made photoflash bombs obsolete.