Four fire engines and around 25 firefighters were called to a fire at an industrial unit on Creek Road in Barking.
The ground floor of a three-storey commercial industrial unit used as a shisha bar was destroyed by fire. One person left the building before the Brigade arrived. There were no reports of any injuries.
The fire is believed to have been caused by ash which was thrown in a bin and ignited combustible materials.
A London Fire Brigade spokesperson said: "Always dispose of ash and smoking materials carefully. Make sure they are out, cold and preferably wet them before throwing into a bin – never use a wastepaper basket."
The Brigade was called at 1259 and the fire was under control by 1359. Fire crews from East Ham, Plaistow, Ilford and Dagenham fire stations attended the scene.