Stormy weather has delayed the start of operations to raise the wrecked Costa Concordia cruise ship, which went down last year with the loss of 32 lives, officials said Monday.

"Due to heavy storms tonight, the operation has been put back by two hours," to 8:00 am (0600 GMT) civil protection chief Franco Gabrieli told a news conference.

He added that there were no changes to the planned operation itself, which is expected to take 10-12 hours once it gets underway.

A last ferry was allowed to leave the Italian Island of Giglio early Monday before the unprecedented salvage operation gets underway. At that stage a maritime exclusion zone will be declared.

The 290-metre (951-foot) long ship has lain on its side ever since foundering off the Tuscan coast on the night of January 13, 2012 in a tragedy that claimed 32 lives.

Salvage coordinators say there will inevitably be some spillage of its waste contents into the pristine Mediterranean waters.

Activists warn thousands of tons of toxic waste will pour into the sea -- but officials say they are ready with extra floating booms and clean-up boats if there is a spill.

The bigger concern for the salvage workers is the resistance of the hull of the ship to the enormous pressures it will have to withstand as it is winched up.

They have however ruled out the possibility of it splitting.