The $450 million Costa Concordia was carrying more than 4,200 passengers and crew when it slammed into a reef and capsized Friday after the captain made an unauthorized diversion from his programmed route and strayed into the perilous waters.
Eleven people have been confirmed dead, their bodies removed from the ship and frigid waters.
Divers were focusing on an evacuation route on the fourth level, now about 18 meters (60 feet) below the surface, where five bodies were found earlier this week, Navy spokesman Alessandro Busonero told Sky TG 24.
Officials restarted the search after determining the ship had stabilized after shifting on the rocks 24 hours earlier.
The ship's sudden movement also postponed the start of the weekslong operation to extract the half-million gallons of fuel on board the vessel, as Italy's environment minister warned Parliament of the ecological implications if the ship sinks.
"Today is an important day, the weather forecasts are negative, rough sea, we'll have to see how the ship reacts to that," firefighter spokesman Luca Cari said Thursday.
Authorities on Wednesday identified the first victim: Sandor Feher, a 38-year-old Hungarian musician working aboard, who a fellow musician said helped crying children into lifejackets, then disappeared while trying to retrieve his beloved violin from his cabin. His body was found inside the wreck and identified by his mother who traveled to Italy, according to the Hungarian Foreign Ministry.
Of the 11 dead and 21 missing, Italian officials have only released 27 names so far. They are two Americans, 12 Germans, six Italians, four French, and one person each from Hungary, India and Peru.
Among the missing are an Italian father and 5-year-old daughter. The girl's mother issued a fresh appeal to speed the search and for passengers who saw the pair to come forward to help determine where they were last seen.
"Don't stop, bring home my daughter. Get her out," Susy Albertini, 28, said on Italian television Wednesday evening after meeting with government and port officials in Tuscany.
Albertini last saw her daughter, Dayana Arlotti, on Thursday when she dropped her off at nursery school in Rimini on Italy's Adriadic coast, according to La Voce di Romagna newspaper. Her estranged husband picked up the girl afterward to prepare for the cruise.
William Arlotti, 36, had taken his daughter on on the cruise with his girlfriend, Michela Marconcelli, who survived. She reported seeing Dayana, who was wearing a lifejacket, slide into the water when the boat shifted, but said someone helped retrieve her, the newspaper reported.
Marconcelli said she was pushed forward onto the life raft, and lost track of her companion and his daughter.
Other missing include retirees Jerry and Barbara Heil of White Bear Lake, Minnesota. The couple were treating themselves after putting four children through college.
The Heil children said in a blog post Wednesday that their parents were not among the passengers whose bodies were recently recovered, and they were praying that weather conditions would improve so authorities could resume search operations.
Capt. Francesco Schettino, who was jailed after he left the ship before everyone was safely evacuated, was placed under house arrest Tuesday, facing possible charges of manslaughter, causing a shipwreck and abandoning his ship.
The ship's operator, Crociere Costa SpA, has accused Schettino of causing the wreck by making the unapproved detour, and the captain has acknowledged carrying out what he called a "tourist navigation" that brought the ship closer to Giglio. Costa has said such a navigational "fly by" was done last Aug. 9-10, after being approved by the company and Giglio port authorities.
However, Lloyd's List Intelligence, a leading maritime publication, said Wednesday its tracking of the ship's August route showed it actually took the Concordia slightly closer to Giglio than the course that caused Friday's disaster.
"This is not a black-and-white case," Richard Meade, editor of Lloyd's List, said in a statement.
"Our data suggests that both routes took the vessel within 200 meters (yards) of the impact point and that the authorized route was actually closer to shore."
New audio of Schettino's communications with the coast guard during the crisis emerged Wednesday, with the captain claiming he ended up in a life raft after he tripped and fell into the water.
"I did not abandon a ship with 100 people on board, the ship suddenly listed and we were thrown into the water," Schettino said, according to a transcript published Wednesday in the Corriere della Sera paper.
Initial audio of Schettino's conversations made headlines on Tuesday, showing an increasingly exasperated coast guard officer ordering Schettino back on board to direct the evacuation, and the captain resisting, saying it was too dark and the ship was tipping.
The officer's order, "Get back on board, (expletive!)" has entered the Italian lexicon, becoming a Twitter hashtag and adorning T-shirts.