Giglio, Italy (CNN) -- The captain of the cruise ship that wrecked off Italy's western coast will be questioned by authorities Tuesday at a hearing, his attorney said.





Francesco Schettino is under arrest and may face charges that include manslaughter, shipwreck, and abandoning a ship when passengers were still on board, according to Italian prosecutor Francesco Verusio.





Schettino could face up to 15 years in prison, he said.





At the closed hearing, a preliminary investigation judge will decide whether Schettino will remain detained. The captain has not yet been questioned, but more than 100 witnesses, including passengers and crew, have been interviewed, the prosecutor said.





The captain's attorney, Bruno Leporatti, said in a statement Monday that Schettino was "shattered, dismayed, saddened for the loss of lives and strongly disturbed."





But, he said, Schettino is "nonetheless comforted by the fact that he maintained during those moments the necessary lucidity to put in place a difficult emergency maneuver ... bringing the ship to shallow waters." That move, Leporatti said, saved the lives of many passengers and crew members.





Italian prosecutors have ruled out a technical error as the cause of the incident, saying the captain was on the bridge at the time and had made a "grave error."





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Late Monday, the head of Italy's coast guard said 29 people remained unaccounted for from the partially sunken cruise ship Costa Concordia -- a sharp spike from earlier estimates of the missing.





Coast guard chief Marco Brusco said the whereabouts of four crew members and 25 passengers were unknown, Italy's ANSA news agency reported.





Authorities earlier believed that 16 people were unaccounted for.





The Costa Concordia hit rocks Friday night just off Italy's western coast, leading to what passengers described as a chaotic and surreal scene to evacuate and the deaths of at least six people.





On Monday, rescue efforts were ongoing in and around the mammoth vessel, which was listing on its side off the island of Giglio.





The search had been suspended earlier in the day because the vessel began to move, said the island's mayor, Sergio Ortelli.





Coast Guard spokesman Filippo Marino said efforts had resumed, adding that rescuers will focus on retrieving the body of a man, presumably a passenger, discovered earlier in the day.





However, he said the weather forecast has rescuers worried, as it calls for rising winds.





The head of the company that owns the ship said Monday he has not given up hope of finding survivors.





"Hope is the last thing to die," said Costa Cruises chairman and chief executive Pier Luigi Foschi. He addressed journalists at an emotional press conference Monday, apologizing repeatedly for the accident.





Prosecutors are examining the ship's data recorder and expect to have results within days, Verusio said.





They are also considering whether others may share responsibility for the crash with the captain.





Foschi placed blame for the wreck squarely on the captain, however, saying Schettino had deviated from frequently traveled routes.





"The captain decided to change the route and he went into water that he did not know in advance," Foschi said.





He said the company was limited in its ability to investigate the incident because it did not have the data recorder.





Schettino, who has been with Costa since 2002, had never been involved in an accident before, Foschi said.





He downplayed the possibility that alcohol may have played a role in the crash, saying he did not believe Schettino drank, and that all crew were subject to random drug and alcohol tests by Costa Cruises.





The company had said earlier that Schettino may have made "significant" errors that led to the wreck.





"The route of the vessel appears to have been too close to the shore, and the captain's judgment in handling the emergency appears to have not followed standard Costa procedures," Costa Cruises said in a statement Sunday.





The ship had about 2,300 tons of fuel on board at the time of the wreck, Foschi said Monday, adding that so far
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