The drilling rig Transocean Winner is being monitored by a counter-pollution team after grounding on the western side of the Isle of Lewis in the Western Isles.
The semi-submersible rig became detached from its tug during a towing operation in the early hours.
Severe weather including high winds prevented the crew of the Alp Forward from reconnecting the tow line.
No-one was on board the rig when it grounded near Carloway, the Maritime and Coastguard Agency said.
A spokeswoman said: “The Maritime and Coastguard Agency’s counter-pollution branch and the Secretary Of State’s Representative for Salvage and Intervention (SOSREP) have both been monitoring the situation since Sunday evening and the local authority, police and Marine Scotland have all been kept informed.
“There is 280 metric tonnes of diesel on board and this situation is being monitored. SMIT Salvage has been mobilised to deal with the incident.”