The source of the deadly poison responsible for killing five dogs that visited Buddina beach on Queensland's Sunshine Coast may never be known, an investigating authority has warned.
It has been a week since vet clinics and dog owners began reporting deaths after visiting the popular area.
The RSPCA said the poisonings could have been one of three ways: intentional, accidental or environmental.
RSPCA communications manager Emma Lagoon said the organisation was exploring several possibilities.
"Someone may have put poison baits out, or it could have been accidental in that someone spilled something like medication through the sand," she said
"Or it could have been environmental such as algae or algae bloom.
"There's a multitude of things that it could be, unfortunately, we haven't been able to determine just yet."
She said while investigators were working hard on the case, there may not be an easy answer.
"It may be a factor that we just simply won't know," she said.
"It's a lot of unknowns at the moment, which is unfortunate, because we want to have some understanding of what's happened so that we can help people in the region."
More dogs present with symptoms
Ms Lagoon said since the initial poisoning reports, more animals have shown similar symptoms.
"I believe there's been four other dogs that have displayed poisoning symptoms that have survived," she said.
"We're just asking people to be cautious at this point when they're walking their dogs, and just making sure that they're not eating or drinking anything from the area that they don't know where it's coming from."
The organisation is working with Sunshine Coast Council on the investigation.
They have ruled out that the toxin came from water bowls in the area.
"Council have cleaned and covered all those water bowls as a precaution," Ms Lagoon said.
"But they haven't reported any findings that they contribute in that area to the poisoning of the dogs."
The group said all the animals were using an off-leash dog area at access 210 on Buddina beach.
"Five of the dogs did attend at some point between the second and the seventh of August," she said.
"So the toxin could be anywhere along the off-lead beach area."
In a statement, Sunshine Coast Council said it had nothing further to report and it continued to liaise with the RSPCA as the lead agency.
Fundraiser launched to help victims
A crowdfunding page has been launched to help cover the costs for the owners of the dogs that have died.
It is aiming to raise $25,000 for the cause.
Organiser Craig Barrass said he hoped it would help in some small way.
"We can compensate them for the veterinary costs, including emergency hospitalisation, tests, medication, euthanasia and funeral expenses," he said.
"It will never mend their broken hearts."
The group is hoping to reach the fundraising target by Sunday when the community will gather for a commemorative walk.
The walk will begin at La Balsa Park at 9am and move onto the beach via entry 201 and down to beach access 210.
The RSPCA is still encouraging anyone whose dog may have been unwell recently and had visited the area to contact them.
Ms Lagoon said people could call the hotline 1300-animal to talk to the RSPCA, the council or vet.
