A series of boat explosions during Fourth of July celebrations injured about 20 people in Georgia and Alabama, according to local and state authorities. The incidents occurred within hours of one another on Friday evening, prompting separate investigations and renewed scrutiny of holiday boating safety. The most serious blast was reported around 7 p.m. on Lake Lanier, about 50 miles northeast of Atlanta. Hall County Fire Rescue said a 23-foot cabin cruiser being towed in Landshark Cove erupted in flames reaching roughly five feet high. Seven people ranging in age from 5 to 45 sustained second- and third-degree burns; four were taken to nearby hospitals by ambulance and a fifth was air-lifted to Atlanta. All were listed in stable condition. The Georgia Department of Natural Resources (DNR) has not yet identified the cause of the explosion. Roughly two hours earlier, a separate vessel exploded on Lake Nottely in Union County, Georgia. Game wardens said the boat had just refueled at Cozy Cove Marina and was idling away when its engine stalled; it blew up as occupants tried to restart it. All seven people aboard were hospitalized with burn injuries, and the craft sank near the shoreline. The DNR is leading that inquiry as well. Across the state line in Dadeville, Alabama, six people were hurt when a pontoon boat that had been converted into an unpermitted fireworks barge malfunctioned and exploded on Lake Martin shortly after 9 p.m. The Alabama Law Enforcement Agency said the victims were treated for burns and other injuries; none were life-threatening. Authorities in both states have opened investigations but have not linked the incidents. While no fatalities were reported, the explosions underscore the hazards that accompany increased traffic, refueling and pyrotechnics on popular waterways during holiday weekends.