Four fire engines and around 25 firefighters tackled a fire at an office on West Quay Walk in Millwall.
One portacabin was destroyed by the fire. There were no reports of any injuries.
Control Officers received 54 calls regarding the blaze. The first was received at 2343 and the incident was over for firefighters at 0041. Crews from Millwall and Poplar fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.