On December 17 a social media post described a pet owner spending a long night with the vet, but all three dogs died.
The post said the dogs had eaten something on the banks of the Manuherikia River at Galloway before becoming violently ill.
However, a later assessment of the river by the Otago Regional Council (ORC) found no sign of toxic algae.
Three days after the incident, resident Sharaya Nikora put up a sign near the track to the river, warning people of the incident, with contact numbers for herself, the regional council and the Central Otago District Council.
She said she contacted the council about signs informing the public, but was told if she felt signs were necessary, she should do them herself.
"My only agenda was if dogs had died from poisoning there was an absolute social responsibility to make sure the public was aware of that," she said.
The owner of the dogs was not a local resident and Ms Nikora wanted to make sure the wider community and visitors to the area knew of the incident.
"[I] took things into my own hands."
ORC signage went up on December 22, but she said the council took too long to put up signs and it was a community health issue.
The ORC signs outlined concerns around toxic algae and freshwater pests.
"Their direction to their [web]sites does little to alleviate worry for others when we still don’t know what killed the dogs."
She said she fielded more than 20 calls from people concerned about the algae over the Christmas-New Year break.
Ms Nikora said people have been thankful for the signs, but she believed the council would remove them.
ORC general manager policy and science Anita Dawe said the regional council had received three public inquiries about toxic algae in the Manuheirkia River between December 17 and 20.
There had been none since then, she said.
The council monitored the Manuheirkia River monthly from sites at Ophir and Galloway and additional weekly samples were taken from the Shaky Bridge during summer.
Ms Dawe said the council could not comment on the legality of Ms Nikora’s sign, but the council does put up warnings and signage on public land and would continue to do so as needed.
The council would continue to educate the public about the risk of toxic algae and had processes in place for the river which became unswimmable, Ms Dawe said.
A CODC spokeswomen said waterways were the responsibility of the ORC and it was not appropriate for the district council to comment.
