Six fire engines and around 40 firefighters tackled a flat fire on Lower Mardyke Avenue in Rainham.
A four-roomed flat on the first floor of a residential block was destroyed by fire. One man left the building with a neighbour before the Brigade arrived and was assessed on scene.
Station Commander Jim Chapman, who was at the scene, said: ""Due to the nature of the fire, the electricity supply to the road had to be shut down whilst crews worked as quickly as possible to make the scene safe."
The cause of the fire is believed to have been accidental and involved a laptop.
The Brigade was called at 1519 and the fire was under control by 1644. Fire crews from Wennington, Hornchurch, East Ham and surrounding fire stations attended the scene.