Five dogs were rushed to a veterinary practice for emergency treatment after suffering suspected poisoning on Hampstead Heath.

The Heath’s police force is investigating after the group of dogs were taken ill in the Sandy Heath area between Wildwood Road and Spaniards Road.

The animals, which were with a professional dog walker, were taken to the Village Vet in Belsize Terrace, Belsize Park, on Tuesday where they were showing signs of poisoning including abnormal behaviour and severe lethargy. They are now said to be doing well.

The news comes after pet owners in Brent were warned to be vigilant by police following the death of three dogs that ate chicken laced with rat poison in March.

Adam Mugford, who is head of emergency and critical care at Village Vet, wrote on Facebook: “The dogs show signs of poisoning with mainly neurological symptoms, signs of abnormal behaviour, loss of control of blood pressure and severe lethargy. Symptoms show rapidly.

“All animals under care are doing well and the cause is still unknown, but we have sent samples to the US for further investigation. More blood tests to be performed later. We will keep you updated.”

The City of London Corporation, which manages Hampstead Heath, warned dog owners to be on their guard and said the Hampstead Heath Constabulary was looking into the matter.

In a series of posts on Twitter, it wrote: “We are investigating reports on this serious matter. No source of poisoning has been found on Hampstead Heath.

“Until we have information to act on, we ask that all dog walkers remain vigilant and report anything untoward immediately to the Heath Constabulary on 020 8340 5260.”

Concerned pet owners have been using social networks to spread the warning.

Sasha Potter, a veterinary nurse, wrote on Facebook: “I think its METHOMYL!! its a highly toxic pesticide and im a nurse at Medivet Hendon and someone is poisoning dogs in parks around Kingsbury and Neasden. Signs are vomiting, salivating, tremors, neurosigns. We have saved a few dogs but many have died because they were too late. The police are involved and its been going on for avout 5 weeks. [sic]”