Florida ? Six people were seriously injured Saturday in a pleasure boat explosion in Florida’s Tampa Bay, authorities said.

The 33-foot, twin-engine Sea Ray exploded and burned to the waterline Saturday afternoon while anchored in 3 feet of water off what’s known as Beer Can Island, according to Gary Morse of the Florida Fish and Wildlife Conservation Commission.

Eleven people were injured, including the six who were flown by helicopter to Tampa General Hospital. Five other children were treated for smoke inhalation and released from the hospital, Morse said.

The cause of the explosion is under investigation. Morse said the boat’s twin engines were not operating at the time, although a gasoline generator was.