Vets in a Surrey town believe anti-freeze poisoning which has caused the deaths of 11 cats in the same road may have been malicious.
The Vets Now clinic in Farnham said it had put five cats to sleep from Eaton Road, Camberley this week and knew of six others which had died.
Four of the animals belonged to the same owner, said senior veterinary nurse, Kath Howie.
Surrey Police said was investigating and had not ruled out foul play.
"We normally see one anti-freeze poisoning case every six months, so to see five in one week and have knowledge of another six cases would lead me to believe this has been malicious," said Ms Howie.
Anti-freeze is highly toxic to cats, which are drawn to the substance because it tastes sweet.
Exposure to a teaspoonful can cause death if they lick their paws after coming into contact with it.
"Unfortunately, by the time the signs of anti-freeze poisoning present themselves it is usually too late to save the cat's life," said Ms Howie.
But she said a life could be saved in the early stages, when the animal's symptoms included staggering, vomiting and being un-coordinated.
In the past few weeks, similar incidents have claimed the lives of 28 cats in Somerset - 19 in Bridgwater and nine in Weston-super-Mare.
A spokesman for Surrey Police said it was aware of a number of incidents in the St Michael's and Watchetts area of Camberley in which cats had died after coming into contact with a harmful substance.
"Local officers are investigating and have not ruled out foul play, but are keeping an opening mind about the circumstances," he said.