Six fire engines and 35 firefighters and officers were called to a fire at a shop with flats above in Commercial Road, Limehouse.
Most of a ground floor storeroom and almost half of the staircase from the ground to the first floor were damaged by the fire. There were no reports of any injuries.
Watch Manager Matthew Hyde, who was at the scene, said: “Crews worked hard in tricky conditions to tackle this fire.
“Part of the staircase had burnt away and it made it more difficult to get to the fire.
“They brought a ladder in through the building and used that to make a safe descent back down.”
The Brigade was called at 0334 and the fire was under control at 0530. Fire crews from Shadwell, Whitechapel, Poplar and Bethnal Green fire stations attended the scene.
The cause of the fire is under investigation.