Officials in Italy are beginning to explore the possibility that the Costa Concordia was carrying unregistered passengers.
The family of a missing Hungarian woman has told officials she was aboard the cruise liner, but there is no formal record of her as a passenger.
Civil Protection Agency head Franco Gabrielli said there could have been more "illegals" on board.
Meanwhile, divers have found the body of another woman, bringing the number of people confirmed dead to 13.
She was on deck seven of the vessel, about 10 metres below the water line.
Twenty people are still believed to be missing. The BBC reports 4200 people were known to be on the ship, which struck a rock in shallow waters near the island of Giglio off the coast of Tuscany on 13 January.
A memorial service was later held on Gigilo for the family and friends of those who were aboard the ship.