Ten fire engines and around 70 firefighters tackled a fire that affected two terraced houses on Guysfield Drive in Rainham.
The roof of one of the houses was completely destroyed and half of the first floor of the house was also damaged, as well as part of the roof of a neighbouring property. Nine people left the house and two surrounding properties before the Brigade arrived. There were no reports of injuries.
The cause of the fire is believed to be a lightning strike during a thunderstorm.
A London Fire Brigade spokesperson said: "The occupants were asleep and were awoken by a loud bang and a fire in the loft space.
"Fires caused by lightning are really uncommon, but unfortunately can cause quite extensive damage.
"Crews worked hard to contain this fire as much as they could, and fortunately no one was hurt."
The Brigade was called at 0005 and the fire was under control by 0152. Crews from Dagenham, Hornchurch, Barking and surrounding fire stations attended the incident.