A new warning is being issued not to go in part of the Maitai River because of the toxic blue-green algae.
This time it is the Avon Tce section of the Maitai River, between Bridge St and Nile St, that has increased levels of cyanobacteria.
The Nelson City Council today urged people to avoid allowing their children to play in or their dogs to swim in that section of the river.
It is the only area of the Maitai River that has exceeded safe levels of cyanobacteria and bathing holes upstream are not currently affected.
In December there was an algae alert in the lower Maitai River from the Maitai Camp downstream.
The council said the naturally-occurring algae was in rivers during this time of year but could bloom to dangerous levels if the conditions were right, with warm temperatures and low river flows.
Cyanobacteria produces the neurotoxin anatoxin, which is potentially lethal to dogs, stock and people when ingested in large amounts. Dogs that are known to eat the algae are most at risk.
Dog owners are advised to keep their dogs on a lead and use the permitted area at Tahunanui Beach to swim.
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