Ten fire engines and around 70 firefighters tackled a fire at an industrial unit being used as a suspected cannabis factory on Devonshire Grove in Peckham.
Half of the single-storey industrial unit was destroyed by fire. There were no reports of any injuries.
A London Fire Brigade spokesperson said: “Cannabis factory fires can be particularly dangerous because of the way criminals use unsafe wiring to illegally obtain electricity in order to grow the plants.
"They're often in top floors or lofts which means when a fire takes hold it spreads, destroying roofs and damaging neighbouring buildings.
"Firefighters can also be exposed to risks when dealing with the fires because of bad wiring and traps at some of the properties.
"It's important that people know the key signs and inform the police so that they can act swiftly to prevent these dangerous fires from happening."
The Brigade’s 999 Control Officers received a call about this incident at 2256 and mobilised crews from Peckham, New Cross, Deptford and surrounding fire stations to the scene. The fire was under control by 0148.
The cause of the fire is undetermined.