Six fire engines and around 40 firefighters were called to vehicles alight in Hainault Recreation Ground, Forest Road, Hainult.
Three vans and one car, which were parked behind food stalls at an event in the park, were damaged by fire. Fire crews removed a number of cylinders from the area as cylinders can explode when exposed to heat.
Approximately 3,000 people were escorted to a safe distance before the arrival of the Brigade. There were no reports of any injuries.
The Brigade was called at 1653 and the fire was under control at 1811. Fire crews from Woodford, Ilford, Dagenham, Leytonstone and Romford fire stations attended the scene.
The cause of the fire is believed to be accidental.