There have been reports of someone leaving poisonous sandwiches in a Beckenham park.
The situation was reported to RSPCA Bromley by a member of public who said the toxic food was being left in Croydon Recreation Ground, Beckenham.
A spokeswoman for the RSPCA said: "These reports are worrying and we would urge anyone with information to report it to us.
"We will investigate every accusation of animal cruelty.
“Anyone found responsible for putting out poison that has caused suffering to animals could face up to six months in prison and a fine of up to £20,000 under the Animal Welfare Act.
"In the meantime we would urge dog walkers and pet owners in the area to be vigilant and anyone with information should contact the RSPCA on the cruelty and advice line on 0300 123 4999."
This comes after three dogs died and three more required treatment when poisoned meat was left in a park in Brent, north-west London.