The NSW Office of Water said yesterday testing had also resulted in high amber alert results for the stretch of the river between Cobram and Moama and for the Edward River at Deniliquin.

Deputy chairwoman of the Murray Regional Algal Co-ordinating Committee Natasha Ryan said while these results were not yet in the red alert range, the results indicated this trigger could be reached quickly.

“Therefore we are issuing a precautionary alert for these areas also,” Ms Ryan said.

The committee has issued a red alert for the algae for the whole of Hume Dam and results on Monday afternoon extended that alert from the dam wall along the length of the Murray River to Cobram.

The red alert level warning indicates the water is unsuitable for recreational use or primary contact by domestic users and may also pose a threat to livestock and domestic animals.

Ms Ryan said town water supply authorities had been informed and were treating supplies with powdered activated carbon for both NSW and Victorian consumers.

She said raw water drawn from these areas should be avoided for all purposes.

“The species of blue-green algae identified are potentially toxic and may cause gastroenteritis in humans if consumed and skin and eye irritations after contact,” Ms Ryan said.

“Boiling the water does not inactivate the algal toxins.”

A department spokeswoman, Bunty Driver, said still and humid weather had promoted growth of the algae which would break up if conditions turned cooler and more windy.

Ms Driver said the conditions were being monitored weekly and the NSW results compared with those taken by the Victorian authorities.

“Our next assessment is due on Friday,” she said.

Ms Driver said four sites on Lake Hume at the dam wall, Ebden and near the Bethanga Bridge had tested positive for the algae and it had also been found in several river backwaters west of the dam wall.

Local residents and visitors have been advised to avoid any water that appears bright green, where obvious green scum is present or a distinctive odour is noticeable.

They have been advised not to enter the water, not to drink untreated water or bathe in water drawn from the river while the red alert warning is in place.

Information updates about algae blooms and red alert areas are available on 1800 999 457 or by visiting water.nsw.gov.au.