A national animal charity has warned dog owners to be vigilant after three pets were poisoned after visiting a park.
The call from the RSPCA comes after the dogs, two bull lurchers and a springer spaniel, were poisoned in Fryent Way, in the Fryent Country Park.
On Thursday March 13 three ate discarded meat, which contained poisonous blue tablets, placed on the grass verge. One of the three died.
The following day on Friday March 14, two other dogs ate poisoned meat placed in the undergrowth. One survived and one died.
Another dog died in January after eating blue tablets in the park.
Simon Osborne, chief inspector for the RSPCA, said: "We are very concerned to hear these reports.
"Poisoning is a cruel and inhumane way for an animal to die and one which would have caused these dogs a great deal of suffering.
"The RSPCA has offered the police any support they need in dealing with these incidents and urges anyone with any information to come forward."
Sergeant Peter Rowntree from Brent Police said: “This is such a nasty, cruel act which has killed three beloved dogs and endangered all domestic pets and wild animals, in such close proximity to a country park.
“Family pets, wildlife and the amenities of a country park are factors that enhance the quality of people’s lives. The owners and families of the dogs affected have suffered acute distress.
“This is not simple, ignorant mischief, but criminal activity and the persons found to be responsible will be prosecuted.”
The poisons, called organophosphates, are found in pesticides.
People are being called to lookout for any unknown substances near the roadside or in undergrowth, particularly any foodstuffs which might contain blue colouring, or any tablets or pellets.