Ten fire engines and around 70 firefighters were called to a fire at a warehouse converted into a temple on Elmwood Road in Croydon.
Half of the building was alight. There were no reports of any injuries.
Station Commander Craig Fenner, who was at the scene, said: "Firefighters worked hard to bring the incident under control.
"One of the Brigade's 64-metre turntable ladders was used at the scene as a water tower to tackle flames from height. Drones were also deployed to provide the Incident Commander with a greater situational awareness of the incident.
"The fire was producing smoke in the vicinity and those who live or work nearby were advised to keep windows and doors closed.
"Elmwood Road remains closed between London Road and Lodge Road, and Wellington Road is closed between Elmwood Road and Saint James's Road. Please avoid the area where possible."
The Brigade's Control Officers took the first of nine calls to the fire at 1309 and sent crews from Croydon, Norbury, Mitcham, Woodside and surrounding fire stations to the scene. The fire was under control by 1612.
The cause of the fire is under investigation.