About £40,000 worth of damage was done to a school by youths who climbed on the roof and destroyed vents.
The young people are believed to have climbed onto the roof at Thornaby Academy, in Thornaby, Stockton and destroyed vents and an air handling unit which controls gas for the kitchen and a hot water boiler.
It means the kitchen at the school on Baysdale Road had to close and flooding damage was caused to some of the classrooms.
The incidents happened on the evenings of 23 and 25 June.
Investigating Officer police constable Katie Lister said: “There is a serious risk of serious injury or death being caused to those climbing on the building due to numerous hazards including electric shock.
“If anyone has information about these incidents they can contact 101 or Thornaby Academy. If anyone is seen trespassing or climbing on buildings, please contact police on 999.”
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