Firefighters were called to a grass fire on a railway bank in the Finchley Road area.
A damaged overhead line caused a short circuit which has caused a grass fire on the railway bank.
The Brigade, British Transport Police and railway staff helped detrain approximately 600 people from two trains stuck on the line. Once everyone was safely off the trains firefighters dealt with the small trackside fire.
One woman was taken to hospital by London Ambulance Service crews.
The Brigade were initially called to the grass fire at 1439 and the incident was over by 1910. Fire crews from West Hampstead and Paddington fire stations are at the scene.