Firefighters were called out to the derelict former Hartwood Hospital near Shotts on Sunday after fire broke out in the main block.
Scottish Fire and Rescue Service sent a total of seven fire appliances to the former psychiatric hospital, after receiving an emergency call at 4.34pm. Firefighters were there within 17 minutes.
They arrived to find a well-developed fire within a large derelict building.
Due to the unsafe condition of the building, crews were unable to conduct internal firefighting operations and proceeded to conduct external firefighting using an aerial rescue pump and main jets.
The fire involved the whole of the roof space and resulted in considerable damage to the derelict building.
This morning (Monday) SFRS reported that the fire had now been brought under control but operations were continuing along with Police Scotland and North Lanarkshire Council representatives, to make the Victorian building safe and crews were remaining in attendance there.
Hartwood closed in 1998 as a result to moves to provide care in the community for those with mental health issues.