Coastguards fear big waves forecast for the next 36 hours could push the ship off its perch, sending it to the bottom of the sea.

The ship's movements are being carefully monitored - and had halted divers' attempts to find the 21 passengers still unaccounted for.

The search has now resumed after being suspended at midnight when laser technology detected the ship was moving, putting search teams at risk.

Firefighters have been working around the clock to find the missing

Authorities said earlier it was too dangerous for divers to enter the vessel and that the search would only resume when it was deemed safe.

The threat of the ship sinking has also raised further concerns of an environmental disaster with the 2,400 tonnes of fuel in the ship expected to pollute the Mediterranean maritime reserve.

As teams try and use heavy-duty cables to secure the Concordia to rocks on Giglio island, a remote-controlled surveillance camera robot has been sent into the ship to continue efforts to find any trace of life.

The movement comes after the stricken ship initially slid by around 5ft (1.5m) deeper into the sea on Wednesday.