Dogwalkers have been warned to keep their pets away from a park after two reportedly died just hours after visiting.
A third dog is believed to have fallen ill while at Millers Park in South London last week, according to posts shared in a local Facebook group.
The exact cause of the mysterious illness is not yet known, but experts have suggested that the symptoms could indicate toxic shock or poisoning.
In a warning to dogwalkers visiting the park, Tender Paws Vets said: "There have been cases of toxic shock after walking/swimming there - which can be fatal."
It then listed a series of symptoms to watch out for, including sudden lethargy, drooling, excessive panting, vomiting, diarrhoea and seizures.
Dog owners noticed the park had been closed as officers collected pond and soil samples, and there have been several social media posts about pets falling ill there.
One said: "My springer spaniel Zebedee was walking in Millers Pond this morning as we do most days.
"A couple of hours later he became ill in the car - projectile vomiting, diarrhoea and drooling. He sadly passed away in my car before I could get him to a vet.
"I have spoken to our vet who sounds like it could be poisoning and toxic shock. Please be vigilant as my heart is broken."
Another person wrote on the page: "There are reports that a second dog has now died after poisoning at Millers Pond in Shirley."
They added in an update: "The owner of one of the dogs that died has said the vet said it's chemical poisoning."
Croydon MP Sarah Jones confirmed the park's closure in a post shared to Facebook last Thursday.
She wrote: "Miller's Pond, Shirley Way is currently closed after reports of several dogs becoming unwell having been in the park.
"The park has been closed to the public, and police and Croydon Parks are currently investigating."
A poster has also been erected near the pond, urging anyone with information to come forward.
It adds: "Croydon Council in partnership with the police are currently investigating recent incidents in which several dogs have become ill after visiting this park.
"While the investigation is ongoing, we have taken the decision to temporarily close the park to ensure the safety and wellbeing of the public and their pets. The park will re-open at the earliest opportunity."
The Met Police said it received a report of a dog falling ill in the park, but has not yet been made aware of any dogs or who have died, nor any criminal activity.
A force spokesperson told MyLondon: "Police were called on Wednesday, March 22 to Millers Park in Croydon after a member of the public reported that her dog had become ill whilst in the park.
"We're aware of some posts on local Facebook groups suggesting two other dogs had also been taken ill and died.
"The local authority and environment agency closed off part of the park to take pond and soil samples to establish if there was any evidence of deliberate contamination.
"Police also attempted to identify any dog owners whose pets had been taken ill; no one has come forward.
"At this stage we're not aware of any dogs having died, or any criminal/ malicious incidents."
Anyone with information which they believe could assist the investigation is urged to contact police on 101, quoting CAD 4203 of March 23, 2023.
