Firefighters were called to a flat fire on Connaught Road in Silvertown.
A balcony on the second floor of the building was destroyed by fire along with various stored items. Part of a three-roomed flat on the second floor was also damaged by the blaze. There were no reports of any injuries.
The Brigade’s Fire Investigators believe the fire was accidental and caused by sunlight being refracted through the bevelled edge of the balcony glass and igniting cardboard boxes stored on the second-floor balcony.
A London Fire Brigade spokesperson said: "On arrival, crews were faced with a well-developed fire on a second-floor balcony.
“The sun is especially strong during these summer months, but fires caused by refracted and reflected sunlight can happen all year round and are actually quite common.
"Our advice is to make sure that you keep mirrors, crystals, glass ornaments and other reflective items out of direct sunlight at all times.”
The Brigade was called at 1101 and the fire was under control by 1157. Two fire engines and around 10 firefighters from Stratford and Shadwell fire stations attended the scene.