Four fire engines and around 25 firefighters were called to a fire at a hospital on Coombe Lane West in Kingston.
A cleaners cupboard on the ground floor of the building was destroyed by fire. Around 300 members of staff and patients left the building before the Brigade arrived. There were no reports of any injuries.
Coombe Lane West was closed between Traps Lane and Warbank Lane whilst firefighters worked to make the scene safe.
The Brigade was called at 1101 and the fire was under control by 1319. Fire crews from Surbiton, Kingston and Wandsworth fire stations attended the scene.
The cause of the fire is under investigation.