Italian prosecutors have opened an investigation into the disappearance of the bell from the capsized cruise ship Costa Concordia.

Franco Gabrielli, Italy's national official for search and salvage efforts, told reporters when he visited Giglio island that the bell disappeared several days ago.

He said a search was on to find the bell, which hung off one end of the ship and was inscribed with the vessel's name. The bell hung off the half of the wreck which is under the sea.

The Concordia struck a reef on January 13 and capsized near Giglio's port.

Salvage crews and divers are working daily in or near the wreckage to remove fuel or search for seven people who are still missing, presumed dead. Twenty-five others died.