A puppy suffered a painful death after swimming in a Hastings park promoted as dog friendly.
Neville Wright said 7-month-old pup Sasha - a Rottweiler Husky cross - swam at Pakowhai Country Park on Sunday afternoon and died on Thursday.
The park, beside the Ngaruroro River's Chesterhope Bridge, is a designated off-lead area for dogs under the control of their owners.
The Raupare Stream flowis through the middle of the park and Mr Wright said most dogs that swam in it kept to flowing water.
"She was swimming amongst the reeds on the muddy side of the river," he said.
"On Monday evening she seemed to start going downhill and I took her to the vet on Tuesday.
"They said take her home and if she is no better bring her back on Wednesday."
Sasha was admitted on Wednesday suffering vomiting and diarrhoea and died on Thursday.
VetServices vet Roger McKinley said Sasha was initially treated for canine parvovirus because of similar symptoms.
"She was suffering and not making any progress so we actually made the decision to put her to sleep," he said.
A post-mortem pointed to toxemia consistent with exposure to blue-green algae but the diagnosis was "not definitive", but because Sasha was only exercised at Pakowhai Regional Park "we are strongly suspicious the source is somewhere there".
When blue-green algae - cyanobacteria - blooms, it can produce toxins which can be harmful to people and animals.
In Hawke's Bay it blooms in the height of summer in nutrient-rich water and can form mats on riverbanks which are usually dark green/brown in colour.
Mr McKinley said it was the likely cause of the death and dog owners should be wary - several dogs have died in Hawke's Bay over the last few years after coming into contact with the algae.
The algae is prevalent in rivers with gravel beds such as the Tukituki, Waipawa, Tutaekuri and Ngaruroro and also poses a risk to people swimming.
Hawke's Bay Regional Council scientists took water samples from the park yesterday.
A council spokesman said he was unaware of any history of blue-green algae at the park and until test results were available dog owners should be wary and supervise their pet closely.
He said dogs should be kept under control and when outdoors owners should take a good supply of fresh water and a bowl for them to drink from, so they were less tempted to drink river water.
Mr Wright said Sasha was "the bounciest, most delightful thing".
"She used to climb trees and jump through windows - people used to say "would you get your dog off me" because she was just too much.
"That's all over now unfortunately."