Salvage crews began preparations on Tuesday to pump thousands of tonnes of fuel from the wreck of the Costa Concordia as the search continued for bodies, 11 days after the giant Italian cruise liner struck a rock off the Tuscan coast and capsized.

Fifteen bodies have been recovered and divers are continuing to search for at least 17 more missing on the 290-metre long vessel, which lies half-submerged on its side just outside the tiny island port of Giglio. Six bodies are so far unidentified.

Dutch salvage company SMIT brought a barge carrying defueling equipment alongside the giant hulk as divers worked on installing external tanks that will be used to hold more than 2,300 tonnes of diesel that must be pumped out of the Concordia.

Navy explosive experts also blasted a hole into the submerged third deck of the ship to allow divers to continue the search of the vessel after the bodies of two so-far unidentified women were found on Tuesday.

While this operation is underway, rescue efforts are continuing simultaneously, fire services spokesman Claudio Chiavacci said.

Authorities have been increasingly concerned at the threat of an oil spill in the marine reserve where the accident occurred but work on removing diesel and lubricant oil has been delayed by the search for survivors and bodies.

Preparations to begin pumping the oil are expected to take several days and the actual work of removing the fuel from the giant liner's 17 fuel tanks will take another 28 days.

The head of Italy's Civil Protection Authority, Franco Gabrielli, said pumping would probably not begin before Saturday.

Anything before that would obviously be welcome, he added.

Officials dismissed reports that oil had started to leak out of the ship, saying that monitoring equipment had shown no significant pollution spreading from the wreck. A thin film of oil had spread in the water but posed no serious threat.

Gabrielli said he had asked the ship's owners Costa Cruises to produce a plan to clean up the pollution from general debris around the vessel by Wednesday.

INVESTIGATION EXTENDED

As the work on Giglio continued into a second week, magistrates investigating the accident are expected to extend their inquiries, with attention increasingly focused on Costa Concordia's operators.

The ship's captain, Francesco Schettino has been blamed for the accident on January 13 and placed under house arrest, accused of multiple manslaughter and abandoning ship before the evacuation of more than 4,200 passengers and crew was complete.

But his lawyer said on Monday that the investigation would be extended to other officials of Costa, a unit of the world's largest cruise operator Carnival Corp.

Costa said on Tuesday it had not been notified that it was under investigation but would cooperate fully with investigators and had full confidence in magistrates.

There was some confusion on Tuesday about the status of toxicological tests on Schettino.

His lawyer said on Monday that the tests had proved negative but Carlo Rienzi, the head of consumer protection association Codacons, which has declared itself a civil party in the case, said drugs tests would be carried out in Rome on Thursday. He said no test for alcohol was planned.

In interviews, the company has placed the blame for the accident squarely on the shoulders of the 51 year-old Schettino, who told investigators he brought the ship close into shore to perform a manoeuvre known as a salute to the island.

How far Costa knew about or even encouraged such manoeuvres has been disputed but there are also questions about when Schettino informed the company of what had happened after the ship was holed by a rock.

Schettino's lawyer has said his client is ready to assume his share of responsibility for the accident but he has said he was in constant touch with Costa's command centre during the including the evacuation of the ship.

(Additional reporting by Cristiano Corvino and Sara Rossi in Milan, Writing By James Mackenzie; Editing by Giles Elgood)