There are concerns that children under 12 years old in Crediton are experimenting with so-called laughing gas - which is highly dangerous.
Youngsters have been seen gathering in a den where nitrous oxide canisters have been found, among the trees in Newcombes Meadow.
There were also empty sweet packets, drink containers, balloons and lighters.
There was also a school book which had been set on fire and would have belonged to a pupil at the junior level.
A local primary school has been informed, along with the police.
The use of nitrous oxide has been a problem in the town for some time - police are warning that it's habit forming and addictive, and can even kill.
Parents are being urged to make sure they know where their children are when not at school.