Firefighters are investigating the cause of a major blaze at Didcot B power station in Oxfordshire.
At its height, 25 fire engines and about 100 firefighters tackled the blaze at the gas-fired station, which broke out at about 20:00 BST on Sunday.
The station was partially shut down, but Energy Secretary Ed Davey said National Grid had assured him that there was no risk to energy supplies.
The fire was extinguished at about midnight and no-one was injured.
Simon Furlong, assistant chief fire officer, said three fire engines were still at the scene on Monday morning and he expected them to be there for at least the next 24 hours.
"This was a serious fire which began in one of Didcot B power station’s cooling towers and spread to three other cooling towers," he said.
"I expect that it will take some time to determine the reasons behind what actually happened."
The blaze began in a cooling tower and spread to three others because of strong wind.
Dave Bray, the fire service’s incident commander, said: "We have extinguished the fire, although there are hot spots that are remaining within the structure.
"It is now the challenge of getting to these and dampening them down."
Mr Bray said firefighters faced "significant challenges" during the blaze because the cooling towers were predominantly made of wood.
An automatic alarm system alerted the fire service, but the first call was actually from a member of the public at Great Western Park in Didcot, he said.