Police are appealing for information after youths were spotted on the roof of the old Noble’s Hospital in Douglas.
Three teenage boys were seen by staff at the Westmoreland Road site at about 5pm on Tuesday.
They fled toward Demesne Road when challenged, but workers found damage to a window a short time later.
One is said to be around 13 years old and was wearing a red football top, with a grey hooded top and dark coloured trousers.
Another wore a dark coloured tracksuit and had a very distinctive hairstyle.
Police would like to hear from anybody who was in the area at the time, or know who could identify the boys.
Anybody with any information can contact police on 631212 or the anonymous Crimestoppers number, 0800 555 111.