The 600 million euro operation ($862 million) to raise the 114,500 tonne ship, the most ambitious salvage of its kind in maritime history, got under way on Monday morning but was expected to continue long into the night after substantial delays, with the salvage team hoping it would be finished in the early hours of Tuesday.

Engineers had said the operation would be completed within 12 hours, but after 10 hours the 290-m-long vessel was still tilted at a dramatic angle, with just a fraction of its submerged hull hauled above the waterline.

There was no hurry to speed up the process - one false move could endanger the whole operation, with the nightmare prospect of the ship breaking up and plunging to the depths.

"We are taking it slowly and very safely," said Sergio Girotto, one of the project's senior engineers.

After keeling over and smashing into the rocky shore on the night of January 13 2012, the ship's now exposed starboard side had suffered "great deformation" and substantial damage, he said.

The ship has to be raised by an angle of 65 degrees, but by sunset it had only been lifted 13 degrees.

Officials expressed cautious optimism that the raising of the Concordia - the biggest passenger ship ever to have capsized - would be a success.

"The game is not over but things are going according to plan," said Franco Gabrielli, the Italian official in command of the operation. "The engineers are being very careful."

"Nothing on this scale has been attempted before. It's unprecedented. But we have here the strongest team of experts that you could assemble," said Roger Frizzell, from Carnival Corp, the American parent company of Genoa-based Costa Cruises, which operated the Concordia.

It was not until three hours after the operation commenced that 5400 tonnes of pressure exerted on the ship by a system of steel cables and winches managed to wrench it free of the two granite spikes on which it has been wedged since capsizing.

As the ship tilts further upright, huge steel compartments on its seaward side will fill with water, with the weight helping to pull the vessel into a vertical position.

LIVE VIDEO: Salvage workers brace for a toxic soup of rotting food, chemicals and other debris as they try to rotate the wrecked cruise ship off the Italian Coast.

Thirty-two people died in the disaster but the bodies of two of the victims have still not been recovered - Russel Rebello, an Indian waiter, and Maria Grazia Trecarichi, a passenger from Sicily who was on the cruise to celebrate her 50th birthday.

Officials said remote-operated, unmanned submarines had so far failed to pick up any trace of human remains.

Survivors of the disaster said the finding of the bodies was a priority.

"Naturally, I think of those people who didn't make it and especially for those two families who are still waiting to find the remains of their loved ones," said Luciano Castro, a 49-year-old journalist who was on the ship when it sank.

"They must still be under the keel of the Concordia and I hope after this finally they will have a grave they can cry over."

The technique used to raise the Concordia, known as "parbuckling", has its origins in the 19th century and entails rotating a sunken ship back to a vertical position. Once the ship is raised upright, it will remain on an artificial seabed made up of six steel platforms and hundreds of sacks of cement.

It will take weeks for it to be patched up and stabilised, by which time winter storms and rough seas will make it too risky to tow it away from the island.

It will not be removed until next year, when it will be taken to an Italian port and broken up for scrap.

For many islanders the ship is a daily reminder of the tragedy and the night on which many of them opened their doors to the bedraggled survivors of the disaster. "Every time we see it lying there, we think of that terrible night," said Renato Iacovacci, 67. "There is still great sadness on the island, but we hope that will begin to heal once they raise the ship and make plans to remove it once and for all."

The technique has been used mainly to recover warships, notably the capsized USS Oklahoma, which was raised by the US military in 1943 after the bombing of Pearl Harbour.

Telegraph, London