French Polynesia's chief prosecutor says three missing people may have been killed with the gun belonging to one of them.
The three are former US professional basketball player, Bison Dele, his girlfriend Serena Karlan, and Frenchman Bertrand Saldo, who have been missing since early July, after stopping over in Tahiti while sailing to Hawaii.
The prosecutor, Michel Marotte, says although no body has been found the signs are that the three are dead as the boat that was found has been cleaned up.
The AFP news agency reports that although no gun was declared when the boat arrived in Tahiti, investigators are reportedly almost certain there was one aboard.
An arrest warrant has been issued for Bison Dele's brother in connection with the incident.
Thirteen members of the FBI are in Tahiti to assist local police in their probe.