An oil rig grounded on a Scots island may have leaked more than 60,000 litres of diesel into the sea.

No pollution has yet been been found after the Transocean Winner broke free from its tug during a storm on Monday and grounded near Carloway on Lewis.

A salvage team was winched aboard on Tuesday and Wednesday and found two of its four fuel tanks had breached.

The vessel was carrying 280 metric tonnes of diesel, around 300,000 litres, but it is unclear how much has leaked into the sea.

The coastguard said on Thursday no pollution has yet been detected in the area and the maximum amount of diesel which could have been lost from the two tanks is 53 tonnes, or 64,000 litres.

Salvage teams are still working to establish exactly how much has leaked into the sea and a counter-pollution aircraft was sent out by the Maritime and Coastguard Agency (MCA) to monitor the situation.

Inspections are expected to continue on the rig throughout the rest of the week and a 300-metre exclusion zone has been put up around the rig to keep boats away from the area.

A statement from the MCA on Thursday said: "There is no pollution detected in the area of the rig and the MCA continue to monitor for any pollution.

"As well as continual observations on scene, the MCA counter-pollution surveillance aircraft yesterday flew over the location and surrounding area to make careful observations for pollution around the rig and the nearby coast and sea and no sheen or sign of pollution has been found.

"Teams from Smit Salvage and Transocean will continue inspections on board the rig this week and the rig remains in the original position.

"Salvors identified two of the four diesel fuel tanks on the rig appear to have been breached.

"It is estimated that the maximum amount of diesel which could have been lost from those tanks is 53 tonnes and salvors will determine the quantity of diesel remaining in those tanks during the course of the salvage operation.

"Diesel is a light and non persistent oil which presents much lower environmental risks than heavy black crude oil.

"Additional salvors and technical experts from Transocean and equipment continue to arrive to the incident area to support the operation.

"A temporary exclusion zone of 300 metres to keep boats away remains in force."