THE owner of two pet cats poisoned by antifreeze described their deaths as the worst day of her life.
Mandy Blackwell said her pets Luigi and Lucky suffered "horrendous deaths" and warned owners of dogs and cats to be extra cautious.
The RSPCA appealed for information, warning the perpetrator could face six months in jail or a £20,000 fine under the Animal Welfare Act if they are caught.
Mandy Blackwell of Church Rise, Undy, said she and children Dale, 16, and Arron, 13, viewed the two cats as "part of the family".
She first realised there was a problem on Thursday, August 23, when Luigi, aged two, began struggling to hold his weight and his back legs were wobbly.
By 3am, he was fitting and his eyes were glazed, so she took him to the out-of-hours service at Marlow's vets, Chepstow.
He died there at 9am, but as Ms Blackwell was at the vet's, her neighbour phoned to say she had found seven-year Lucky fitting under her car.
Ms Blackwell said: "It was the worst day of my life, I felt like my family was being massacred."
The vet suspected antifreeze poisoning, with Lucky dying later that day and a neighbour's cat called Pabi was also a victim.
Ms Blackwell added: "We are distraught, I can't imagine how anyone could be so cruel to innocent animals. I just want people to be extra cautious with their cats and dogs."
The RSPCA carried out post-mortems, which showed they died from anti-freeze poisoning.
A spokesman said some household brands of antifreeze can cause agonising deaths for cats. Symptoms include appearing drunk and sleepy, increased breathing rate, vomiting and seizures.
RSPCA inspector Gary Lucas said the organisation urgently needs more information on the poisonings, adding: "There may be an innocent explanation to these sad deaths, but we are concerned someone is deliberately causing suffering to cats."
Call the RSPCA cruelty and information line on 03001234999 with information.