An oil rig grounded on Lewis could be refloated by the beginning of next week, it has been revealed.

The Transocean Winner was carrying 280 metric tonnes of diesel when it ran aground on the western side of the island on August 8.

Two of its four fuel tanks were damaged in the incident, resulting in the loss of up to 53,000 litres of fuel and sparking fears of marine pollution.

On Saturday, engineers transferred the remaining oil from the rig's pontoon tanks to a safer position above sea level.

It is now hoped that a transfer from the higher tanks to the supply vessel Olympic Orion should be completed within the next 24 hours.

Following the transfer, a decision will be made as to whether the operation to refloat the rig will commence within the next 48 hours.

Dave Walls, operations director with Transocean, said on Friday: "We need to get ourselves in the position where we're ready to float and we're not there yet.

"Once we're ready to float we then need the ideal conditions to float - and that's a suitable weather window, no wind, the right tide.

"Everything needs to be just right because we get one opportunity to do it right."

He vowed no trace of the rig would be left when the salvage operation - including a sweep of the seabed - is complete.

A Marine Accident Investigation Branch investigation has been launched into the incident.