The operation to uplift an oil rig that ran aground in the Western Isles could be put on hold over winter.

The Transocean Winner grounded near Carloway on Lewis during a storm on August 8.

It was towed to Broad Bay on the far side of the island two weeks later and plans are in place to transport the 16,000-tonne rig to Turkey, where it will be dismantled.

Attempts to move the rig have been hampered by bad weather and Transocean has been asked to make preparations in case it is forced to remain in Broad Bay over winter.

The latest bid to relocate the Transocean Winner began on Wednesday and salvage experts hope to move it on to the back of the OHT Hawk later this week.

A new vessel will have to be brought to replace the 60,000-tonne Hawk in if the operation is not completed by Monday, when its contract expires.

A second heavy-lifting vessel has been identified but the project would be delayed by at least two weeks while new arrangements are made.

Salvage expert Hugh Shaw, who is overseeing the exercise, said: "Potential weather windows for the operation are beginning to reduce very rapidly now.

"Although we are considering alternative loading locations, the success of any loading wherever it takes place is diminishing with the approach of winter.

"With this in mind, I have asked Transocean to look at other contingencies including a plan for maintaining the rig in Broad Bay over the winter if it becomes necessary.

"We know that the rig can be safely secured there if needed.

"At the moment, though, I remain hopeful that this weather window will be sufficient for the operation to take place."

Two of the Transocean Winner's four fuel tanks ruptured in the collision and spilled about 53,000 litres of diesel into the sea. Most of the oil is believed to have dispersed harmlessly.