Firefighters have put out fires at the derelict Strathmartine Hospital near Dundee after suspected wilful fire raising.
Police are now investigating the “multiple fires” and suspect that they were started deliberately.
Emergency services were called to the abandoned site, which sits on the border of Dundee and Angus, shortly before 7pm and had the fire extinguished after an hour.
A Police Scotland spokesman said: “There were multiple small fires within derelict buildings.
“It is being treated as a crime – suspected wilful fire raising.”
The site, previously a hospital and orphanage for people with learning difficulties, has been empty for 15 years but has been regularly targeted by vandals and people starting fires.
A Scottish Fire and Rescue Service spokeswoman said: “We were called to a fire within a derelict building at the hospital.
“Two breathing apparatus and one hose reel were in use.
“We received the report at 18.57 and the stop message from crews at 19.59.
“Police were in attendance.”