Questions abound for captain of doomed cruise ship

• NEW: Authorities on land ordered the captain to return to the ship, a newspaper reports
• Costa Cruises says "there may have been significant human error" on the captain's part
• Attorney: The captain's move to bring the ship to shallow waters saved many lives
• Schettino might be charged with manslaughter and abandoning ship with passengers on board

Rome, Italy (CNN) -- Of the 4,200 people on board the doomed Costa Concordia, perhaps only one man knows exactly why the ship veered close to land, crashed into rocks and tumbled onto its side, leaving at least six people dead.

That man, Captain Francesco Schettino, is under arrest and could face charges including manslaughter, shipwreck, and abandoning a ship when passengers were still on board.

Schettino, who goes before a judge for a closed hearing Tuesday, could face up to 15 years in prison, Italian prosecutor Francesco Verusio said.

He appears to have given Coast Guards contradictory and confusing information about what was happening in the hours after the collision, according to a partial transcript printed Tuesday in an Italian newspaper.

Authorities in the port of Livorno seem to believe he had abandoned ship with passengers still on board, the Corriere della Serra report suggests.

"You must get back on board.... You have to coordinate the rescue operation. Commander, this is an order," the unnamed Coast Guard tells Schettino, the paper reported.

"I'm in charge. You have abandoned ship and now you are going to the (ship) and coordinate the work," the report says.

The newspaper does not say how it obtained the transcript, which it did not print in full, but prosecutor Verusio confirmed that it matched one which prosecutors were using in their investigation.

Prosecutors and the cruise line both blame the captain for the disaster.

"Preliminary indications are that there may have been significant human error on the part of the ship's Master, Captain Francesco Schettino, which resulted in these grave consequences," Costa Cruises said in a statement.

"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," the statement added.

The Italian Coast Guard is investigating why Schettino went so close to Giglio Island, off Italy's western coast, on Friday night.

Corriere della Sera reported that Schettino came close to Giglio to salute Mario Palombo, a legend among Costa cruises' commanders, and as a gesture to the only Giglio native on board, chief steward Antonello Tievoli.

Sailors call sailing past a place for the benefit of a crew member a "bow," according to Corriere della Sera.

Costa Cruises chief executive Pier Luigi Foschi was asked Monday if Schettino was making a salute to the island.

"Yes," Foschi said.

But Schettino has denied the assertion that he had steered the ship too far toward land.

"We were about 300 meters (1,000 feet) from the shore, more or less," Schettino said after the accident.

Speaking on Italian television, Schettino insisted the rocks were not marked on his map.

"On the nautical chart, it was marked just as water," Schettino said.

But the Italian Coast Guard insisted that the waters where the ship ran aground were well-mapped. Local fishermen say the island coast of Giglio is known for its rocky sea floor.

"Every danger in this area is on the nautical chart," Coast Guard Capt. Cosimo Nicastro said. "This is a place where a lot of people come for diving and sailing. ... All the dangers are known."

Local authorities and residents said they believe that after sustaining damage from what it struck, the ship sailed at least half a mile north, and the captain turned it around toward land, where it toppled.

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.

Questions also linger about whether the captain should have ordered an evacuation sooner and why no "mayday" distress signal was sent.

Thousands have voiced their support of or anger toward Schettino on social media.

A Facebook page supporting the Schettino had more than 2,300 "likes" on Tuesday, but several pages openly denounced the captain.

Schettino joined Costa cruises in 2002 as a safety officer, served as a staff captain and was appointed captain in 2006, according to the cruise line. Like all Costa masters, the cruise line said, Schettino "has been constantly trained, passing all tests."

Schettino had never been involved in an accident before, said Costa Cruises chairman and chief executive Pier Luigi Foschi.

Foschi also 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.

On Tuesday, the coast guard said it has located the second "black box," or data recorder, from the ship and that operations were underway to retrieve it, said coast guard Warrant Petty Officer Massimo Macaroni.

Information from the device, along with that from another that has already been recovered and is being analyzed by prosecutors, will provide authorities with "a complete picture of how the disaster unfolded."

CNN's Dan Rivers, Brian Walker and Josh