Brent police and the RSPCA have launched a fresh appeal for information after three dogs died after being poisoned in park in Kingsbury.

Another two dogs required medical treatment after ingesting meat left in Fryent Country Park, by Salmon Street, covered with a carbamate insecticide.

The lethal substance was analysed by experts and identified as Methomyl – which has been banned in the UK due to its toxicity.

Last month, Lesley Hastings of Glenwood Grove, Kingsbury, told the times that she had lost her six-year-old Lurcher called Toby after he ingested the poisoned chicken.

Her eight-year-old Jack Russell cross Maisie who ate a small amount survived, and her third dog Lucy did not come into contact with the poultry so was unaffected.

Ms Hastings said: “I noticed them eating something and at first I thought it was mouldy bread but at closer inspection I realised it was cooked chicken with bright blue paste on it so I took it away.

“When I got home Maisie started convulsing so I took her to the vets, I didn’t even think about Toby. By the time I returned home he had died.

“He’s a big dog and it killed him in just 30 minutes.”

Fears have emerged that the poisoner may have moved on to Hampstead Heath after five animals were taken ill last week.

The pets, who were with a professional dog walker, were rushed to a veterinary practice where they received emergency. They were said to be showing signs of poisoning including abnormal behaviour and severe lethargy but are now “doing well”.

RSPCA chief inspector Simon Osborne said: “This kind of poison is extremely toxic for dogs and other animals if consumed and it is very concerning to hear that this is what caused the recent deaths.

“We urge anyone who knows of any person who has a stock of this particular insecticide at home or in even their shed or garage to talk the Police or ourselves in complete confidence, so we can investigate further.”

Pet owners are being warned to be on their guard and wear gloves if handling any substances.

No arrests have been made and enquiries continue.

Sergeant Peter Rowntree from Brent Police said: “Officers from Fryent Safer Neighbourhoods Team have been carrying out extra patrols in and around the park. I am grateful to everyone who has assisted to raise awareness regarding these incidents and I would encourage all dog walkers and the users of any of our parks, to be vigilant and phone through any suspicious activity. With better weather and longer hours of daylight the parks will be busier and I am hopeful that any criminal activity is more likely to be seen and phoned through to us.”

A Natural England spokesperson said “It’s distressing and disturbing to think that somebody could be using such a dangerous toxin so indiscriminately. We would encourage anybody with any information on these incidents to contact Brent Police immediately.”

If anyone has any information they are asked to call 101 or Brent Council, Animal Welfare on 020 8937 5256.