Diesel oil leak from grounded rig Transocean Winner
Two fuel tanks on the grounded drilling rig Transocean Winner have been breached, releasing an unknown amount of diesel oil.
The Maritime and Coastguard Agency (MCA) said the rig at Dalmore beach, a beauty spot on the Isle of Lewis, was carrying 280 metric tonnes of the oil.
It said two out of four tanks holding the oil appeared to have been damaged.
UK government official Hugh Shaw said there was no evidence of oil around the installation or on the beach.
He said the fuel may have been lost during the grounding and then dispersed at sea.
The Scottish government said it was "closely monitoring" the situation, although the UK government has responsibility for managing such incidents.
Mr Shaw, the Secretary of State's Representative for Maritime Salvage and Intervention who is overseeing the salvage operation, said monitoring for oil was being done from the shore and from the air by aircraft.
He said counter pollution measures were ready and available if oil was detected.
The rig was being towed from Norway to Malta when the tug towing it got into difficulty in bad weather on Sunday evening. The tow line is understood to have broken in the early hours of Monday.
Deputy First Minister John Swinney has contacted UK government officials to question why the rig was being towed when stormy conditions were forecast.
The MCA said it was unclear how much fuel had been "released into the environment".
The apparent breaches in two of four fuel tanks were noted during an assessment made by a team from Smit Salvage and Transocean on Tuesday.
The squad was able to assess three of the four tanks. Mr Shaw said it was not known if all the fuel the rig was carrying had been lost.
Bad weather has prevented the team of eight from returning to the rig, which ran aground on Monday morning after a tow line to a tug broke.
The MCA said: "The rig remains in the original position and was reported to be carrying 280 metric tonnes of diesel oil on board in total split between a number of separate tanks.
"During the inspection the salvors discovered that two of the fuel tanks appear to have been breached, however, it is unclear at this time how much oil from those tanks has been released to the environment.
"Weather conditions have made it impossible for the team to continue the assessment today."
A temporary exclusion zone of 300m to keep boats away remains in force.
The Western Isles Emergency Planning Co-ordinating Group met on Wednesday and reinforced appeals for the public to avoid the area. which is popular with surfers and visitors to Lewis.
Only emergency vehicles and local residents are allowed to use the Dalmore village road and the area is being monitored for animal health issues.
Scottish Environment Secretary Roseanna Cunningham said it was "obviously concerning" that fuel tanks appeared to have been breached.
She said: "Although the diesel is expected to rapidly disperse in the current sea conditions, the environment group, which is chaired by Marine Scotland, has put in place measures to swiftly identify any potential environmental impact on this precious and fragile marine habitat.
"This whole incident raises serious questions about why this rig was being towed through Scottish waters when such stormy conditions were forecast, and the deputy first minister has been in direct contact with the UK government about this very point."