Bega Valley Shire Council’s manager of health and building services, Jeff Tipping, said the overflow had been caused by the influence of heavy rain on council waste management infrastructure.

He said it usually took from 48 to 72 hours for water to return to a safe condition after an overflow although sometimes it could take a week or more.

NSW Fisheries had been informed about the overflow and had advised against swimming or fishing in the lake, he said.

Council has posted advisory signs around the lake to alert lake users.