GIGLIO, Italy (CNN) -- The capsized cruise liner Costa Concordia was sitting upright early Tuesday after the first step of an unprecedented effort to salvage the ill-fated ship.
In a lengthy process involving massive pulleys, cables and steel tanks, a salvage crew managed to roll the 114,00-ton vessel off of the rocks where it ran aground in January 2012 as it passed the Italian island of Giglio. Once righted, the Concordia sported a sharp, slashing line separating the white paint of the exposed hull from the brownish muck that had collected on its submerged starboard side.
"It was a perfect operation, I would say," said Franco Porcellacchia, the head of the technical team for the cruise line Costa Crochiere, owned by American firm Carnival Cruises.
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The effort began at 9 a.m. Monday (3 a.m. ET). By midnight, despite delays for thunderstorms and for slack in a crucial cable, the ship had been hauled off the rocks and upward about 25 degrees -- far enough to start drawing water into the massive steel boxes attached to the side of the hull, using the weight of that water to finish rolling the hulk onto a steel platform built off the sea floor.
It took only four more hours for the wrecked ship to come to rest on the platform.
The Costa Concordia disaster killed 32 of the 4,200 people on board. The remains of two victims, Russel Rebello of India and Maria Grazia Trecarichi of Sicily, never have been recovered.
Once the hull was peeled off the rocks, operators sent robotic cameras to survey the damage but found no sign of bodies. But there also appeared to be no sign of leaks, Franco Gabrielli, the head of Italy's Civil Protection agency, told reporters -- a promising sign, as the wrecked liner is full of spoiled food and chemicals including paint and lubricants.
Rebello, 33, was a cruise waiter who was last seen helping passengers off the ship. Trecarichi was on the cruise to celebrate her 50th birthday with her 17-year-old daughter, who was one of thousands of people who survived the deadly shipwreck.
A complex operation
The nearly $800 million effort is the largest maritime salvage operation ever, according to Reporters and sightseers lined the port and the hillsides to watch as the work began.
It sounds counterintuitive, but in order to salvage the Costa Concordia, crews worked to sink portions of it deeper underwater.
The process that began Monday is known as parbuckling, in which cables began to haul the 952-foot ship upright. It's become a household term in Giglio, the tiny island that was transformed when the Costa Concordia ran aground.
The ship is being rotated onto giant platforms 30 meters (about 98 feet) below the water level. Areas of the ship that have been dry for months will be submerged and filled with water.
A ship this large and this heavy has never been parbuckled before. Normally, crews would blow up the ship or take it apart on site -- a cheaper route than what's being done now.
But officials say that's not an option with the Costa Concordia, because the ship is filled with noxious substances, and because there are two bodies still believed to be either trapped between the ship and its rocky resting place or somewhere deep in the ship's hollow hull.
Technicians and salvage managers from all over the world will be watching closely to see what goes wrong and what works.
"It will set the new standard for maritime salvage," Giovanni Ceccarelli, the project's engineering manager, told CNN.
Hundreds of people and dozens of companies have collaborated on the preparations, but the parbuckling will come down to 12 people, including the salvage master and specialized technicians, who will be guiding the operation from inside a prefabricated control room set up on a tower on a barge in front of the ship.
In preparation for Monday, tall towers had been anchored onto the rocky shoreline between the ship and the island have been fitted with computer-operated pulley-like wheels.
When the rotation began, the wheels guided thick cables and chains pulling the middle third of the ship from under its belly toward Giglio. At the same time, more chains and cables attached to the sponsons welded onto the ship's port side pulled the ship from the top toward the open sea.
After passing the 20-degree mark, gravity takes over and the ship essentially finishes the process, relying on the sponsons alone to control the speed at which it rights itself. Technicians will need to pump compressed air into the boxes to control the water levels, which will create buoyancy to slow the ship's rotation until it eventually comes to rest on makeshift "mattresses" put in place on the steel platforms.
If all goes well, the ship won't separate
or break apart. If things go wrong, it could be disastrous.
Noxious substances, other items on board
The ship contains a mix of chemicals that would be devastating for the environment if leaked into the water, which would happen if the ship breaks apart or sinks.
According to the Costa Concordia's inventory list published in the Italian press and confirmed by Costa, thousands of liters of thick lubricants, paints, insecticides, glue and paint thinners were on board before it set sail three hours before it crashed.
There are also 10 large tanks of oxygen and 3,929 liters of carbon dioxide.
That's not all.
Refrigerators filled with milk, cheese, eggs and vegetables have been closed tight since the disaster.
And the freezers that have not burst under the water pressure are still locked with their thawed, rotting contents sealed inside, including 1,268 kilograms of chicken breasts, 8,200 kilograms of beef, 2,460 kilograms of cheese and 6,850 liters of ice cream.
But as the ship rotates, much more water will enter it than will spill out, salvage operators say. That fresh seawater will dilute some of the toxic mix, but it will all eventually have to be purified and pumped out before the ship is towed across the sea for dismantling at its final port -- a location that remains to be determined.
In the meantime, the salvage operators have set up two rings of oil booms with absorbent sponges and skirts that extend into the water to catch any debris that may escape.
Once the ship is upright, it will be months before the contents are removed, probably not until it reaches its final port.
At that time, Costa officials say they intend to remove personal effects from the staterooms and return those to each passenger, no matter how soggy. None of that is expected to happen before next summer.
Meanwhile, Francesco Schettino, the captain who guided the ship off course, faces charges of manslaughter, causing a maritime disaster and abandoning ship with passengers still on board. His trial resumes in Grosseto on September 23.
A turning point
Once the ship is upright, the salvage operation changes dramatically.
A tiny robotic submarine with surveillance cameras will survey the damaged side of the ship and create models needed in planning for the next phase of operations.
"It will look like a high-impact car accident when it is lifted," Nick Sloane, the salvage master, told CNN. "It won't be pretty."
For days, salvage workers have been running simulations and testing their equipment. A steady hum of machinery out on the wreckage site could be heard night and day in Giglio harbor.
The ship looks nothing like it did months ago, when it seemed gigantic against the tiny island.
Now giant cranes, barges and generator towers dwarf the wreckage.
Success or failure, no matter what happens Monday, the Concordia will never again look the same.
Barbie Latza Nadeau and CNN's Livia Borghese reported from Giglio. CNN's Matt Smith reported from Atlanta. CNN's Ed Payne contributed to this report.