Italian rescuers suspended efforts to find survivors Monday as the hulk of a giant cruise liner slipped in worsening weather on the steep rocky underwater slope on which it is lodged off Italy's west coast.
Earlier they recovered a sixth body from the 114,500-tonne Costa Concordia, which was holed by a reef Friday night and rolled onto its side just off the coast of the picturesque island of Giglio. In addition to the six known to have died, officials say 16 of the 4,200 passengers and crew are missing.
The vessel's captain, Francesco Schettino, was arrested on Saturday and has been accused of manslaughter and abandoning his ship before all those on board were evacuated.
The chief executive of the ship's owners, Costa Cruises, on Monday blamed human error by Schettino for the disaster. Pier Luigi Foschi told a news conference the company would provide its captain with any assistance he required. "But we need to acknowledge the facts and we cannot deny human error," he added.
The calm weather which since Friday has aided the rescue and search of the wreck, one of the biggest ever, took a turn for the worse with rougher seas and a light drizzle falling.
In mid-morning fire brigade spokesman Luca Carli told reporters: "There was a slippage of 9 cm (4 inches) vertically and 1.5 cm horizontally. We evacuated immediately. This is something we have been worried about.
"Operations are suspended. We will have to monitor the stability of the ship and we don't know when we will resume operations," he said.
A salvage expert on Giglio, who asked not to be named, told Reuters the ship was clearly moving after being held in place by sharp points of rock that had pierced the hull. Rougher seas could break it free, which would be a "big problem," he said.
Carli of the fire brigade said the rescuers could hear no noises from possible survivors inside the half-submerged ship.
"Obviously the more time passes, the less possibility there is of finding anyone alive," he said.
Cruise company chairman Foschi said Schettino's actions had caused the accident and were contrary to company rules. The captain denies being too close to the coast and says the rock he hit was not marked on charts.
His lawyer, Bruno Leporatti, said Schettino was "overcome and wants to express his greatest condolences to the victims."
But he said Schettino's actions in anchoring the ship at one end to swing it closer to the shore after the collision, "saved the lives of thousands of people."
"It could have been an enormous tragedy," Leporatti added.
The United Nations' shipping agency, the International Maritime Organization, said it was important not to pre-judge the outcome of an inquiry but said it would examine changes to regulations if these were shown to be necessary.
Recalling the sinking of the Titanic in April 1912, IMO Secretary-General Koji Sekimizu said: "In the centenary year of the Titanic, we have once again been reminded of the risks involved in maritime activities."
Even before the wreck of the Costa Concordia moved, the rescue had been hampered by heavier seas.
A diver working to search the vast dark spaces inside the multi-storey liner told Reuters: "The sea is rougher today. It is much more difficult to work."
The disaster occurred as passengers were sitting down to dinner Friday night, triggering panic with thousands jostling to get on lifeboats and some leaping into the icy sea.
Investigators say the vessel was much too close to the shore and residents say its course was much nearer land than usual.
The father of the ship's head waiter told Reuters that his son had telephoned him before the accident to say the crew would salute him by blowing the ship's whistle as they passed close by Giglio, where the both the waiter, Antonello Tievoli, and his 82-year-old father Giuseppe live.
"The ship obviously came too close," the elder Tievoli said. "I don't know if Antonello asked the captain to come near, but the responsibility is always the captain's."
Passengers say there seemed to be unexplained delays in sending an SOS and organizing the evacuation of those on board and this had resulted in chaos. More than 60 people were hurt.
Italian passengers told newspapers they used their mobile phones to call the Carabinieri police in the city of Grosseto on the mainland to raise the alarm, while the crew were still insisting to them that there was only an electrical fault.
Three people, a South Korean honeymoon couple and a crewman, were rescued Sunday and police divers also found the bodies of two elderly men, still wearing life vests. The bodies of two French tourists and a Peruvian crewman were found Saturday.
The vast hulk of the 290-metre vessel, lying on its side, loomed over the little port of Giglio, which sits on the island of the same name in a maritime nature reserve off the Tuscan coast.
A large gash could be seen in its hull but salvage experts said its fuel tanks did not appear to have been damaged, lessening the danger of an oil spill in the pristine waters.
A sixth body, that of an adult male passenger, was recovered just before dawn Monday, officials said.
Giuseppe Linardi, the national government prefect for the province of Grosseto, told reporters the number of those unaccounted for stood at 16 but that could change slightly as passenger lists were rechecked.
He said efforts to prevent an environmental disaster would have to wait until the rescue was over.
"The worsening of the weather could create a critical situation," he said. Forecasters said heavier seas were on the way.
Workers from Dutch salvage company Smit said equipment to pump fuel off the stricken liner was being sent by barge but the operation would depend on it remaining stable.
The ship is resting in about 20 meters (60 feet) of water but could go down by up to 130 meters if it becomes detached from the rocks.
Investigators were working through evidence from the equivalent of the "black boxes" carried on aircraft to try to establish the precise sequence of events behind the disaster, which occurred in calm seas and clear weather.
Carnival Corp, the ship's parent company, said it estimated the impact on its 2012 earnings for loss of use alone to be around $90 million. Its share price was down nearly 16 percent on the London market.
Italy's defense minister, Giampaolo Di Paola, who is also an admiral, said the disaster did not appear to have been caused by natural or technical factors.
"In my estimation there was a serious human error, which had dramatic and tragic consequences," he told RAI state television.
Prosecutors accused Schettino, who has worked for Costa Cruises since 2002 and who was promoted to captain in 2006, of refusing to return to the vessel when asked by the coastguard.
Schettino said the ship hit rocks that were not marked on maps and were not detected by navigation systems. He said the accident occurred some 300 meters (yards) from shore.
There was deep anger in Italy about the accident.
In a frontpage editorial for the respected daily Corriere della Sera, Pierluigi Battista wrote: "Italy owes the world, international public opinion, the families of those who lost their lives, those who were injured and those who fortunately remained unhurt, a convincing explanation and the toughest possible sanctions against those responsible for this tragedy."
(Additional reporting by Silvia Ognibene, Silvia Aloisi and Kate Hudson)