SUSPECTED blue-green algae has been found at the Loch of Clickimin in Lerwick.
Notices have been posted on footpaths next to the loch warning against contact with algal scum.
Adjoining landowners have been advised, as have Scottish Environmental Protection Agency, NHS Shetland and Shetland Anglers Association.
Confirmation should come today (Friday) on whether it is indeed blue-green algae.
The algae can sometimes cause skin rashes, eye irritations, vomiting, diarrhoea, fever and pains in muscles and joints, while it is known to have killed livestock and dogs.