Six fire engines and around 40 firefighters were called to a fire at an outbuilding on Gerpins Lane in Upminster.
A small container holding cabling was destroyed by the fire. A small part of the roof and a van were also damaged. One man was taken to hospital by London Ambulance Service crews.
The Brigade was called at 1808 and the fire was under control by 1849. Fire crews from Hornchurch, Wennington, Dagenham, Harold Hill and Romford fire stations attended the scene.
The cause of the fire is under investigation.