Fire investigators believe a spark from machinery triggered the huge fire that swept through Europe's biggest biomass power plant yesterday.
Firefighters spent more than 15 hours tackling the fire at the Tilbury power plant on the banks of the River Thames in Essex.
The damage is understood to be widespread and fire chiefs believe it will take a further two days to remove the embers of the wood pellets that fuelled the blaze.
The power plant operators RWE npower say it is too early to determine the full extent of the damage but the emergency shutdown has at a stroke removed 10% of the UK's renewable energy capacity.
Chief Fire Officer David Johnson, the initial Incident Commander, said that firefighting operations were hindered by the fact that the fire was high up in the main structure of the building, making it difficult for crews to reach it.
He described how the whole of the building was heavily smoke logged and crews were assisted by a police helicopter in devising a tactical plan to look at the safest possible way of getting special foam onto the fire to suffocate oxygen from reaching the flames.
The fire involved between 4,000 and 6,000 tonnes of wood pellet fuel in storage cells - at least two of the bunkers were destroyed in the fire.
CFO Johnson described how firefighters had to isolate several high-voltage power cables that were affected by the fire.
Tilbury B began full operation in 1969 and, until early 2011, operated as a coal-fired power station with the capacity to generate 1,131MW of electricity for the National Grid.
In early 2011, RWE npower was granted the necessary consents from the Environment Agency and Local Planning Authority to convert all three of the power station’s units to generate power from 100% sustainable biomass.
With a capacity of 750MW, the converted plant provided enough power for around 1.5 million households over the remainder of its lifetime.
Last week, the operators of Drax, the UK's largest coal-fired power station in North Yorkshire, said they were shelving plans for a dedicated 290MW biomass power plant at its Selby site because the £700 million investment was no longer financially viable.
The UK has signed up to achieve a legally binding target of 15% of its energy from renewable sources by 2020. The Department of Energy and Climate Change estimates as much as half of that may be generated from biomass, which includes municipal waste, wood pellets and straw.
A spokesman for RWE npower said last night: “We will investigate the cause of the incident and the extent of the damage to the station but our priority in the meantime is to work with the emergency services on site.”
In a statement this morning, a spokesman for Essex Fire Brigade, added: "Firefighters are continuing to remove pellets from the hoppers while at the same time maintaining a foam blanket on the affected hoppers to prevent the fuel from re-igniting."