Go paddling in Otago rivers but "steer clear" of anything that looks black and slimy, the Otago Regional Council advises, in the wake of toxic algae being discovered in the Silver Stream at Mosgiel.
The algae, found on sticks and vegetation in the Silver Stream, is believed to have killed two dogs, and walkers and dog owners have been warned to stay out of the waterway.
Council environmental information and science director John Threlfall said a search of other waterways, including the Taieri at Outram Glen, failed to discover any signs of the algae.
"That does not mean it is not in the lower Taieri.
There could be a small amount there we could not see."
With most Otago rivers at very low flows, people needed to be aware the algae could be there and not to get it on their hands or near their face, he said.
The region's river levels have continued to fall due to a second consecutive week of little rainfall.
Eastern and northern Otago rivers had been most affected by the lack of rain, and all, were either below or well below normal, the council's weekly rainfall and river report said.
Minimum flows have been reached along the Taieri River and in further north, along the Kakanui and Shag Rivers.
