Salvage teams have succeeded in lifting the hull of the shipwrecked Costa Concordia from the Italian reef where it has been stuck since it capsized in January last year.

They are now cautiously optimistic they can rotate the luxury liner upright and eventually tow it away.

Never before has such an enormous cruise ship been righted, and the crippled Concordia did not move for the first three hours after the operation began. But after 6,000 tons of force were applied using a complex system of pulleys and counterweights, it moved from the reef.

Engineer Sergio Girotto said the cameras did not reveal any sign of the two bodies that were never recovered from among the 32 who died when the Concordia slammed into a reef and capsized after the ship's captain steered it too close to Giglio Island.

Images transmitted by robotic diving vehicles indicated that the submerged side of the hull had suffered "great deformation" from all its time on the granite seabed, battered by waves and compressed under the weight of the ship's 115,000 tons, Girotto said.

The initial operation to lift the Concordia from the reef moved the ship just three degrees toward vertical, leaving the vessel 62 degrees shy of being pulled upright. While a seemingly small shift, the movement was significant enough to be visible: A few feet of slime-covered hull that had been underwater became visible above the waterline.

Engineers were waiting for the operation's completion before declaring success: The entire rotation was expected to last as long as 12 hours, with teams prepared to work into the night if need be.

So far, "rotation has gone according to predictions," and no appreciable pollution from inside the ship has spewed out, said Franco Gabrielli, chief of Italy's Civil Protection agency, which is overseeing the operation.

Giglio is part of a Tuscan archipelago in a marine sanctuary where dolphins and fish are plentiful.

The operation, known in nautical parlance as parbuckling, is a proven method to raise capsized vessels. The USS Oklahoma was parbuckled by the US military in 1943 after the Japanese attack on Pearl Harbour.

But the 1,000-foot, 115,000-ton Concordia is the largest cruise ship ever to capsize and required the complex rotation.

The operation involves engineers using remote controls to guide a synchronised system of pulleys, counterweights and huge chains looped under the Concordia's hull to nudge it free from its rocky seabed and rotate it upright.

During the rotation process, a series of tanks fixed on the exposed side of the hull will be filled with water to help pull it down.

Once the ship is upright, engineers hope to attach an equal number of tanks filled with water on the other side to balance the ship, anchor it and stabilise it during the winter months. The flat-keeled hull itself will be resting on a false seabed 100 feet underwater, made out of a platform and cement-filled sandbags that fill in the gaps of the sloping, jagged reef.

When it comes time to tow the ship in spring, the tanks will gradually be emptied of the water so the ship becomes buoyant enough to float off the seabed, working like a giant pair of water wings.

The Concordia's captain is on trial for manslaughter, causing a shipwreck and abandoning the ship during the chaotic and delayed evacuation. Francesco Schettino claims the reef was non the nautical charts for the liner's week-long Mediterranean cruise.

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