Four children were taken to hospital after they ate sweets thought to contain cannabis.
Ambulance teams were called when some of the children, aged 12 and 13, started vomiting and falling in and out of consciousness in Epsom on Saturday.
Two medical students nearby assisted in the early stages, police said.
Surrey Police said said it did not have a clear description of the sweets but they were reported as green jelly circles called “jelly apple rings”.
Officers have asked parents to warn their children about the dangers.