A health warning for the Ashley River has gone unheeded amid confusion over what part of the river is safe and who is responsible for signage.
The warning, given by both the Canterbury District Health Board (CDHB) and Environment Canterbury (ECan) from January 18, concerns potentially toxic blue- green algae (benthic cyanobacteria) found in the river at Rangiora, near the Loburn Bridge.
Members of the public are advised to avoid "contact recreational activity" and prevent dog access to the area.
Canterbury medical officer of health, Dr Alistair Humphrey, said the algae looks like dark brown to black mats and can produce toxins harmful to people and animals.
"Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips."
An ECan spokesperson said the algae had been found on the Loburn side of the river and a sign there warned people about it.
She said people should also be cautious about swimming on the Rangiora side.
However this was not made clear in the CDHB press release on its website or on the Ecan website or Facebook page which concerned the "Ashley River - Loburn Bridge".
It was up to either ECan or the Waimakariri District Council to put up signs to inform swimmers of the warning, a CDHB spokesperson said.
When the Northern Outlook visited the Rangiora side of the river on Monday afternoon, there were several people swimming, with many saying they were unaware of any warning.
Leanne Pascoe had brought her daughter and a friend to the river for a dip and said it would be a concern if the condition of the water had not been made clear.
She said her family had been swimming there all holidays.
"If it wasn't safe, then we'd all be sick."
Nanny Fran Brodtmann, 24, had brought children in her care to the site.
She had not seen any signs and believed the site to be perfectly safe.
Waimakariri District Council environmental manager Les Pester said ECan, CDHB and the council had a monitoring and response protocol.
He believed that under the protocol, ECan rangers would update signage.
The Waimakariri District Council was responsible for ensuring signage was up to date and he would be asking ECan staff to make sure this happened at the Ashley River, Loburn Bridge site.
- (Live Matches)