Four teenagers are recovering after they shared a cannabis-infused gummy bear at a school dance shortly before Christmas.

Three of the four were taken to hospital by ambulance and assessed by doctors. The fourth was cared for at home by her parents, according to a release from Sarnia police.

Bluewater Health could not comment on what treatment included, but police confirmed the girls were released from hospital the same evening.

"It was just one big gummy bear apparently," said Const. Giovanni Sottosanti with Sarnia police. "Maybe an adult would have been fine or someone who had been a previous user of cannabis that understood the effects, but for these girls it affected them so bad they were fearful for their health and wellbeing."

However, associate medical officer of health with Windsor-Essex County Health Unit, Dr. Wajid Ahmed, said even a grown person may have issues if they consume too much due to not seeing effects right away.

"The effect is not very quick. It takes some time for the cannabis to show its psychoactive effects," he said.

"And sometimes people when they're consuming cannabis, they don't realize how much they have already consumed before they start to see the psychoactive effects."

According to police, one concern is that the quantity of THC or other products in the edible is unknown to the consumer and could have serious, long-lasting effects.

"We don't know if there were any other drugs in that edible and we haven't been able to confirm exactly where that edible came from either," said Sottosanti. "It scared the parents and the school quite significantly."

Sarnia police are reminding the public that illicit cannabis-infused edibles are illegal.

The teenagers and their families have agreed to work with the Sarnia Police Service to understand the consequences of these actions through community programs.

Ahmed said the health unit is waiting to see how cannabis content in edibles would be regulated in the province.