Police are appealing for information following a suspicious fire at the former Strathmartine Hospital.
The blaze, just north of Dundee, started between 6pm and 7pm on Sunday and it was extinguished by the Scottish Fire And Rescue Service.
The cause of the fire has been confirmed as deliberate by the fire service.
Fire officers are following a positive line of inquiry but they would like to speak to anyone who can help the investigation.
The emergency service has stressed that people are placing themselves at risk of injury by accessing derelict buildings like the hospital.
Anyone with information should contact Police Scotland on 101 or anonymously on Crimestoppers on 0800-555111 with the reference CR/7655/19.