A fish farm barge carrying 170 tonnes of fish feed and 1,000 litres of diesel fuel has sunk near Lochboisdale on South Uist.
It was overwhelmed by heavy seas and is now lying in 20m (65ft) of water.
Salmon farm operator Mowi said there was no evidence of fuel or feed escaping from sealed containers on the barge.
The company plans to have the fuel removed safely later this week. No-one was on the barge when it sank.