COPS have been forced to apologise to a British mum after they swooped on the family home in Bradford searching for a cannabis factory and instead found an electric heater keeping two pet guinea pigs warm, the Yorkshire Evening Post reported yesterday.

Pam Hardcastle, 42, said officers from West Yorkshire Police obtained a search warrant and mounted a raid on her family's home when they thought they had uncovered a specialist heating system designed to grow cannabis.

Elevated heat levels recorded at the property by a police surveillance helicopter sparked the raid, but instead of drugs, cops found her 10-year-old son's two guinea pigs - named Simon and Kenny - cuddled up in the garage in front of a heater.

Ms Hardcastle said a police inspector had visited her to issue an apology in person.