Thirteen children at a north London school were taken to hospital when they fell ill after eating what they believed were "sweets".
The pupils from La Sainte Union Catholic School, Highgate, were taken by ambulance to hospital for treatment just after midday.
Police said the sweets were believed to contain tetrahydrocannabinol (THC), an active ingredient of cannabis.
Investigations are under way to establish the quantity in each sweet.
No-one is believed to be seriously unwell and the children's parents have been informed.
No arrests have been made but inquiries have begun to establish what happened.
The school, which is a girls' Roman Catholic secondary, has not been evacuated.
A spokesman for the school said: "The students became ill after eating what they believed were sweets.
"The contents of what the students ate and how they came into possession of them is being investigated by the police.
"We have made parents aware of this incident."