Italian officials investigating the calamity ordered the vessel's return to port so it can be thoroughly searched for other possible victims, and for evidence into the cause of the fiery disaster.
The Bari prosecutor leading the Italian inquiry, Giuseppe Volpe, fears the Italian-owned, Greek-operated ferry may still hold the bodies of illegal immigrants and other passengers who died in the accident, but were not accounted for in the provisional death toll.
Ettore Cardinali, the investigating magistrate working under Volpe in the case, made an initial inspection of the Norman Atlantic on Friday afternoon, during which he was able to recover the vessel's "black box" data recorder.
Cardinali told reporters as he left the ferry that movement around the ship was limited, but that he planned additional daily sweeps starting Saturday.
"For the moment, it's not possible to enter the garage deck of the ferry for safety reasons," Cardinali said.
Volpe has said almost 500 people may have been aboard the Norman Atlantic -- far above the 474 officially on the manifest. Italian authorities have been cross checking names of the 477 survivors with official lists of passengers who embarked on the ill-fated Greece-Italy crossing.
Volpe said it had been "established" that illegal immigrants were aboard the ship, something confirmed by several rescued passengers. Among the undocumented voyagers on the Norman Atlantic were two Afghan political exile-seekers, and another from Syria.
Investigations on the ferry are expected to concentrate on the car deck where the fire started, and where parked cargo trucks may have contained untold numbers of hiding illegal migrants.
Given the possibility that stowed-away illegal immigrants -- or passengers who could not manage to escape their cabins when the disaster broke out -- may remain caught inside the ferry, Italian authorities continue referring to the current death total of 13 as provisional.