Four fire engines and 21 firefighters and officers were called to a fire in a high rise building on Marsh Wall, Millwall, E14 on Saturday evening.
An en-suite bathroom in a two bedroom flat on the 19th floor of the 44 floor building was damaged by the blaze and one person escaped before crews arrived.
The Brigade was called at 1910 and the fire was under control by 1949.
Fire crews from Millwall, Shadwell, Whitechapel and Dowgate fire stations attended the scene.
The fire is believed to have started when cardboard boxes ignited after being stored too close to a spotlight within a shower cubicle.
A London Fire Brigade spokesperson said: “"Some spotlights generate a lot of heat and can set fire to flammable material if they are placed too close to it and left on. Keep spotlights well away from material such as cardboard, window coverings, such as curtains, blinds and drapes, as well as bedding, clothing and fabric.”