Thousands of litres of diesel are feared to have spilled into the ocean from an oil rig that ran aground on the Western Isles in severe weather.
Checks found that two of the fuel tanks on the Transocean Winner rig have been breached but the Maritime and Coastguard Agency (MCA) said it is “unclear at this time” how much oil from the tanks has escaped.
The rig was carrying 280 tonnes of diesel — more than 300,000 litres — when it was blown ashore in severe weather conditions on the western side of the Isle of Lewis early on Monday.
The semi-submersible rig detached from its tug during towing and the weather prevented the line being reconnected.
A “low level” of pollution was detected by tests on Monday, Western Isles Council said, but no obvious signs of a spill remain at the site.
Hugh Shaw, the UK government’s representative for maritime and salvage, said the area is being scoured by aircraft for any signs of a slick further out in the Atlantic.
No-one was on board the rig when it grounded at Dalmore beach near Carloway.
Salvage teams were winched on board by helicopter on Tuesday to assess the damage but have been unable to return due to the weather.
The diesel was being stored in four tanks on the rig, two of which have been damaged.
People are being urged to stay away from the beach as teams continue to work and a temporary 300-metre (980ft) exclusion zone has been set up at sea.
Environmental groups have raised concerns, while it is expected to take “some time” to re-float the rig as it came ashore at high tide with a storm surge.
An MCA spokeswoman said: “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.
“Additional salvors and technical experts from Transocean, and also equipment, continues to arrive to the incident area to support the operation.”
Scotland’s Environment Secretary Roseanna Cunningham said serious questions need to be asked as to why the rig was being towed during severe weather.
“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,” Ms Cunningham said.
“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.”
Friends of the Earth Scotland said it could create a “serious problem” for vital wildlife, tourism and fishing in the area.
Director Dr Richard Dixon said: “If the diesel oil leaks into the environment, the clamour for answers as to why such a risky trip was attempted will grow much louder.
“Lessons from this incident will need to be learnt, and quickly, with further decommissioning of North Sea rigs expected and climate change expected to create more powerful storms and difficult seas.
“The rapid reinstatement of the Emergency Towing Vessel that was based at Stornoway could go some way to alleviating the concerns of communities in this area.”
PA