The Environmental Protection Agency has launched an investigation after an articulated lorry spilt a load of vegetable oil into a river at Barnesmore Gap.
The 40-foot lorry landed on its side and slid into a roadside drain at the picturesque site between Donegal Town and Ballybofey.
The driver managed to escaped with cuts and bruises.
However, a quantity of the reprocessed oil, which was being transported in buckets and drums, ended up in the Lowerymore River.
Donegal County Council immediately launched a salvage operation and engaged two private contractors to assist with the clean-up operation.
The clean-up was headed up by a specialist pollution response and remediation company engaged by the insurers of company who owned the material spilt.
Inland Fisheries Ireland was also alerted to the spillage which took place at 3.30pm on Wednesday afternoon.
Officers then deployed booms in the river to catch any material released downstream and to monitoring its impact.
A spokesman said there has so far been no evidence of fish deaths as a result of the spillage.
Council staff and the various specialist contractors worked quickly to contain the oil emerging through the culvert from the vehicle’s load.
The operation continued the early hours of Thursday to unload the truck, retrieve and collect any vegetable oil released and ensure that only minute traces of the vegetable oil entered the river.
The vehicle was lifted and removed at approximately 3am, with the assistance of An Garda Siochana to manage traffic flow, and the clean-up continued until all materials were removed.
The operation was concluded on Thursday afternoon, although booms remain in place in the Lowerymore river, at a number of strategic locations, to provide continued protection from residual material which may remain lodged in vegetation along the course of the river.
Inspections of the lower parts of the river has indicated that the clean-up operation has been a success.
There has been no evidence of any traces of the vegetable oil in Lough Eske and the River Eske as it flows out of the lake.
The incident has been reported to the Environmental Protection Agency and ongoing monitoring and investigation continues.
