Two men were airlifted Monday morning to Jackson Memorial Hospital's Ryder Trauma Unit after a boat explosion on Stock Island, authorities said.
The incident was reported just before 9:30 a.m. in a channel just offshore of Stock Island Marina.
Monroe County Fire Rescue officials said four people were aboard the 32-foot Contender when the explosion took place.
William Parker, 53, of St. Augustine and boat owner Wendal Lynn, 42, of Waynesboro, Georgia, were airlifted to the hospital with burn injuries.
Authorities said two other men, Ronald Miller, 34, and Don Mosely, 55, both of Lyons, Georgia, suffered minor injuries, but declined treatment at the scene.
Authorities believe the explosion might have been caused by Parker lighting a cigarette, which ignited gas fumes.
The boat had just stopped at the marina gas station for about 85 gallons of fuel, according to an incident report by the Monroe County Sheriff's Office.
Monroe County's deputy fire marshal and the state fire marshal are investigating the incident.