A fire at a British power station close to London has affected the station output, operator RWE npower confirmed Monday.
The fire broke out in one of the cooling towers at Didcot B power station in Oxfordshire on Sunday evening.
The blaze was brought under control after two hours. No injuries were reported, but a power generation unit is now closed.
In a statement, RWE npower said: "The module supplies cooling water to one of the two generating units at Didcot B so 50 percent of the station output has been affected at this moment."
"The affected part of the power station was immediately and safely shut down, and all employees accounted for."
The incident did not pose a danger to public safety, RWE npower added.
The Oxfordshire power station supplies a million homes with electricity. The fire could exacerbate Britain's already constrained electricity supply as winter approaches and energy demand rises.
RWE said the cause of the fire was not yet known and it was too early to tell how long the unit will be out of operation.
"The affected part of the site will remain non-operational until an investigation and repairs can take place," said RWE.
Reports said Britain was already at risk of an electricity supply shortage as the country's capacity margin - the spare capacity available for planned and emergency use - could fall below 5 percent this winter, which would push up wholesale electricity prices.
Police advised nearby residents to stay indoors and keep windows and doors closed.
However, Oxfordshire chief fire officer Dave Etheridge said that the smoke plume was not thought to pose a public health risk.
"There is absolutely no risk to the public from the smoke plume and we are confident there will be no effect on electricity," he said.
"It was a very serious fire and we are working very hard in very difficult conditions."
RWE npower is a Britain-based electricity generator and supplier of gas and electricity to homes and businesses.