Around 70 firefighters tackled fire in East London which broke out on grassland.
Authorities were called just before 2pm to the blaze in two large areas on Lambs Lane in Rainham, and 10 fire engines attended.
The flames covered nearly six hectares of grass and took firefighters over two and a half hours to bring under control.
Residents in the area have been advised to keep their windows and doors closed to avoid the smoke.
A statement from the London Fire Brigade said: "Ten fire engines and around 70 firefighters were called to a grass fire on Lambs Lane in Rainham.
"Firefighters tackled a grass fire where nearly six hectares of grass were alight.
"The Brigade was called at 1343 and the fire was under control by 1617. Fire crews from Dagenham, Hornchurch, Barking, East Ham and other surrounding fire stations attended the scene.
"Firefighters will remain at the scene for the next few hours to dampen down the area.
"The cause of the fire will be investigated."
The London Ambulance Service said: "We were called today (10 August) at 2.24pm to reports of a fire on Lambs Lane, Rainham.
"We have sent a number of resources to the scene including an incident response officer and members of our hazardous area response team (HART).
"The incident is ongoing and we are working with our emergency service colleagues."
The fire is just a mile from where a large blaze in Wennington on 19 July destroyed 16 homes, with crews fighting to save the fire station itself from the flames.
The National Fire Chiefs Council has warned UK cities they need to prepare for wildfires after dozens of “unprecedented” blazes broke out during last month’s record breaking temperatures.
London’s fire chief has called for a “total ban” on disposable barbecues as the capital braces for a second summer heatwave.
The warning comes after the LFB experienced its “busiest week” in history last month.
London’s Fire Commissioner Andy Roe said “urgent action” was needed to introduce a national ban on the sale of disposable barbecues which he warned could cause “untold damage”.
Firefighters attended more than 1,000 fires in the week from 18 July as temperatures soared, taking more than twice as many calls as usual and tackling an unprecedented number of large grassland fires.
During that period the brigade received 8,302 calls, while on average it usually takes around 450 calls a day.
Roe said people behaved “carelessly” and “recklessly” despite warnings about grass fires.