It added it was grateful to the ambulance service for holding handovers, as well as to the fire service for their “swift and professional” response.
Nottinghamshire Fire and Rescue Service confirmed it was called to the hospital at 20:28 GMT.
“A fire was located in the structural void and was extinguished using one hose reel jet,” a spokesperson said.
A structural void is a gap between two walls or ceilings within a building, but it is not yet known what caused the fire.
The spokesperson added: “Once extinguished, crews revisited the site periodically throughout the night to reinspect and ensure no further heat sources were present.”