Eight fire engines and around 60 firefighters tackled a fire at a residential block of flats on Mizzen Street in Barking.
A four-roomed flat on the sixth floor of the seven-storey building was mostly destroyed by fire. Around 50 people were led to safety from the building by firefighters, with one adult man and one adult woman taken to hospital by London Ambulance Service.
The fire is being treated as accidental and is believed to have been caused by the catastrophic failure of lithium batteries that were being charged in a bedroom.
A London Fire Brigade spokesperson said: "Lithium batteries store a significant amount of energy in a very small space and are much more powerful compared to other types of batteries. If that energy is released in an uncontrolled way, then a fire or explosion may result. If there is overheating, crushing, penetrating or overcharging, then a fault can occur within damaged battery cells which may cause the battery to catch fire and/or explode.
"Fires involving lithium batteries, which power devices, can be ferocious, producing jets of flame. The blaze is also hot enough to melt through metal. This type of fire produces a highly flammable, explosive and toxic vapour cloud which should never be inhaled. The fire can also be extremely challenging to put out. Our advice is to get away to safety and call 999.
"Lithium batteries, or the devices powered by these batteries, should be stored and charged in a location away from where people live, such as in a shed or a garage. If they have to be stored inside, make sure there is smoke detection fitted, it’s kept it in a room where you can shut a door and contain a fire and your means of escape is not obstructed. Never store or charge on an escape route such as a hallway or by an exit to a property.
"It is also important to ensure that you buy your batteries from a reputable seller and to ensure you are using the correct charger for the batteries."
The Brigade's 999 Control Officers took over 10 calls to this incident, with the first call received at 0046. Control Officers mobilised crews from Barking, East Ham, Plaistow and surrounding fire stations to the scene. The fire was under control by 0148.