The cause of a fire at the Olympic Park’s energy centre in Stratford last night remains a mystery.

Four fire engines and around 20 firefighters tackled a blaze on the North Plaza at around 10.30pm.

The flames started in a container filled with about 100kg of dry wood ash.

Crews, from Homerton and Leyton, managed to prevent the fire from spreading and it was confined to the container. It was under control by 2am today.

The energy centre was completed in October last year. During the Games, it will provide a low-carbon heating and cooling system for venues in the Olympic Park.

A spokesman for LOCOG, which manages the site, said the centre was empty at the time of the fire.

He said: “It was dealt with quickly and safely and there was no permanent damage.

“We are working with the London Fire Brigade to investigate the cause.”