Four fire engines and around 25 firefighters were called to a flat fire on Newland Street in North Woolwich.
Part of a three-roomed flat on the second floor of the building was damaged by fire. Three people left the building before the Brigade arrived and were all treated on scene by London Ambulance Service crews.
The Brigade’s Fire Investigators believe the fire was accidental and caused by lithium-ion batteries for an electric bicycle.
A London Fire Brigade spokesperson said: “Batteries can present a fire risk if they’re over-charged, short circuited, submerged in water or damaged, so it’s really important to protect them against being damaged and charge them safely.
"Unplug devices once they have finished charging and always make sure you use the right charger for your device.”
The Brigade was called at 1932 and the fire was under control by 2044. Fire crews from Plaistow, East Ham, Poplar and Barking fire stations attended the scene.