Twenty fire engines and around 125 firefighters responded to a flat fire on Belgrave Walk in Mitcham.
A row of townhouses converted into flats were involved in the fire. The fire spread across all three floors and into the roof spaces of the buildings. There are currently no reports of any injuries.
Assistant Commissioner Pam Oparaocha said: "Firefighters worked tirelessly in arduous conditions to bring this fire under control during what has been a very hot day.
"Although the fire is now under control, firefighters will remain at the scene this evening tackling hot spots and carrying out damping-down operations to ensure the fire is fully extinguished. We continue to ask local residents to keep their doors and windows closed while crews remain on scene, as some smoke may still be present. Please also continue to avoid the area.
"Crews are carrying out a systematic search of all the affected buildings, supported by the Brigade's drone capability to search areas that are difficult to access. One of the Brigade's 32-metre turntable ladders has also been deployed as part of the firefighting operation, allowing crews to tackle the fire safely from height.
"Around 35 residents have been displaced, and a rest centre has been established at a local church. Our Community Engagement team is at the scene, working closely with partner agencies to support those affected by the incident.
"I would like to thank our firefighters, Control officers and all the staff who have worked tirelessly throughout this incident. Their professionalism and dedication have been exceptional, particularly in such challenging conditions."
The Brigade took the first of over 60 calls reporting the fire at 1510. Control Officers mobilised crews from Sutton, Wallington, Wandsworth and surrounding fire stations to the scene. The fire was under control by 1752.
The cause of the fire is under investigation.