Six fire engines and around 40 firefighters have been called to a grass fire just off the Green Man Roundabout end of Wanstead Flats in Leytonstone.
Around two hectares of grass and shrubs are alight.
The Brigade's 999 Control Officers have taken 35 calls to the fire.
Station Manager Brin Powell, who is at the scene, said: "Crews are working very hard to tackle the fire, using hoses and fire beaters.
"Bush Road has been closed and is likely to remain closed for sometime, but Blake Hall Road remains open. There is congestion in the area.
"During the hot weather we are attending a large number of grass fires across London so we are again asking the public to take care not to drop cigarettes or matches on dry grass and to keep a very close eye on barbecues.
"Dropped glass can also start fires as the sun can magnify the sun’s rays.
"Grass fires can quickly spread and cause serious damage, so if you see grass smouldering, please call 999 immediately.”
• Never leave camp fires or barbecues unattended and extinguish them properly after you have finished using them
• Clear away bottles, glasses and any broken glass to avoid them magnifying the sun and starting a fire
• Dispose of smoking materials such as cigarettes safely
• Explain to children the dangers of playing with and lighting fires
The Brigade was called at 1352. Fire crews from Leyton, Woodford, Walthamstow and Homerton fire stations are at the scene.