A fireworks display on the Blue Creek section of Lake Martin, Alabama, erupted in an explosion late Thursday during Independence Day celebrations, prompting authorities to declare a mass-casualty incident. Witness video shows a blast on a dock shortly after the show began, injuring an undetermined number of attendees gathered on boats and shoreline properties. Emergency officials dispatched several medical helicopters and ground crews to evacuate the wounded to regional hospitals. Law-enforcement agencies have cordoned off the site and urged boaters to stay clear while investigators work to determine the cause of the blast. No fatalities have been confirmed, and officials said they will release injury figures and additional details once families are notified and the scene is secured.