Up to 53 tonnes of diesel spilled into the sea from the Dalmore oil rig.
A pollution spotter plane swept the coastline and sealochs looking for signs of a slick.
Any trace of diesel entering Loch Roag could contaminate salmon growing in fish farms.
The aircraft flew between Tarbert and Shawbost, also covering around Loch Roag with "absolutely no pollution detected," said Hugh Shaw, the UK Government's maritime salvage representative.
Most of the diesel is said to have been broken up by rough seas and evaporated.
Mr Shaw has set up a base in Stornoway to monitor the operations.
Unfavourable weather prevented salvage experts from boarding the stranded semi-
53 tonnes of diesel lost from Dalmore rig
11 August 2016
Once we get the teams onto the installation we'll continue with the checks on the fuel tanks," said Mr Shaw.
The Transocean Winner ruptured at least two of her four fuel storage tanks crashing into rocks after breaking her tow in wild seas on Monday.
Another tank is intact while inspectors could not access the fourth.
The 33-
Teams from Smit Salvage and Transocean will continue inspections on board the rig once the weather is suitable.
Fuel storage tanks in the base of the rig were ruptured, spilling diesel into the sea
The rig remains in the original position at Dalmore beach.
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.
The tug Union Bear -