NASSAU, Bahamas – Authorities in the Bahamas are trying to determine what caused a fire on a tour boat in an incident that killed a U.S. citizen and injured nine people.

Royal Bahamas Police Force Superintendent Shanta Knowles says officials from the country’s police, fire and civil aviation departments were on the island of Great Exuma on Monday conducting an investigation into the explosion and fire.

Knowles says there were 12 people on board when the incident occurred Saturday a few minutes into a day trip around the small islands near Great Exuma. Photos show the boat engulfed in smoky flames that forced the 10 U.S. citizens and two Bahamian crew members to jump overboard.

The U.S. Coast Guard airlifted four Americans to Florida for treatment while six people were treated in Nassau.