Six fire engines and around 40 firefighters tackled a fire at a community hall on Main Road in Romford.
Half of the roof of the single-storey building was damaged by fire and a caravan was destroyed. Around 27 people left an adjacent residential block before the Brigade arrived. There were no reports of any injuries.
The Brigade was called at 0052 and the fire was under control by 0219. Fire crews from Harold Hill, Romford, Hornchurch, Dagenham and surrounding fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.