THE fire at Didcot Power Station that took 22 hours to put out was caused by a spark during demolition work.
Firemen were called to tackle a blaze at the decommissioned station at 4.30pm on Wednesday.
Crews only managed to finally put the fire out at 2pm yesterday.
The fire in a transformer unit was caused by a stray spark from demolition crews cutting through metal piping.
Oxfordshire Fire and Rescue group manager Richard Smith said the job had taken so long because the transformer was housed in a large steel cage.
He said: “The transformer is mainly made of copper but is impregnated with oil.
“The problem we had is getting access to it.”
At the height of the fire, three fire crews were called in.
Mr Smith said: “There was absolutely no danger of it spreading at all, it was completely contained within the decommissioned site.”
Demolition contractors Coleman and Company used their machinery to cut into the steel cage to give firefighters better access. Coleman said it has now launched an investigation into the cause of the fire.
Coal-fired Didcot A power station is currently being demolished, with three of the six cooling towers due to be blown up on Sunday, July 27.
Nick McHugh, spokesman for plant owner npower, said: “There have been no injuries and the fire service managed the incident with support from the onsite team.
“This incident is in a different location to the southern cooling towers.”
The Environment Agency (EA) said it had been liaising with npower and the fire service to ensure any risk to the environment was minimised.
Spokeswoman Elisa Orchard said: “The run-off from fire water was fully contained.
An EA officer attended and will continue to advise the site operator on managing any ongoing risks.”
Didcot A was shut down in March after 42 years to meet an EU directive to cut carbon emissions. Gas-fired Didcot B continues to operate.
npower announced the July cooling towers demolition date on Monday but refused to give an exact time, partly out of health and safety fears if thousands of spectators gather to watch, but also because the demolition is partly dependent on weather conditions on the day.