Salvage crews have entered the final phase of recovering the wrecked Costa Concordia cruise liner, authorities have said.

Maritime engineers said late on Monday they finally hit the tipping point after 15 hours of slower-than-expected progress in pulling the 114,500-ton Concordia to an upright position, after crews lifted it from a rock shelf earlier on Monday. 

The luxury liner was raised by 25 degrees just before midnight on Monday, after which the effect of gravity started giving the rotation a boost, engineer Franco Porcellacchia said.

"This is considered an important milestone because at this point we don't need anymore the strand jacks to rotate the vessel, but the rotation of the vessel will be guaranteed," Porcellacchia said.

The most complex and costly salvage operation of its kind ever attempted began at 9am local time (0700 GMT) on the Italian island of Giglio after a three-hour delay due to an overnight storm, and progress was slower than originally estimated.

Still on its side, the flank of the ship was entirely off the rock shelf and raised far enough out of the sea to reveal a dirty brown water mark staining the white hull.

"The ship is reacting very well because it's rotating in a uniform fashion, which is what we expected but it's a pleasure to see it confirmed," said Franco Porcellacchia, leader of Costa Cruise's technical team.

Bodies never recovered

Never before has such an enormous cruise ship been righted, and the ship did not budge for the first three hours after the operation began, engineer Sergio Girotto told said.

He said the cameras did not immediately reveal any sign of the two bodies that were never recovered from among the 32 people who died on January 13, 2012, when the Concordia slammed into a reef and toppled half-submerged on its side after coming too close to Giglio Island.

The project has cost $800m and insurers for ship owner Costa Crociere, who are picking up the bill, estimate it could be $1.1bn.

Islanders whose lives have been turned upside-down by the wreck said they were relieved that the time when the ship will finally be removed was drawing closer.

They will have months more to wait, as the towing away is not planned until spring of next year at the earliest when the ship will eventually be scrapped.

Prayers were held in a local church on the eve of the operation on Sunday for the salvage.

Source: Al Jazeera and agencies