A fire inside a nuclear power station took firefighters seven hours to extinguish yesterday.
Emergency plans were put into effect as more than 45 firemen tackled the blaze at the Sizewell B station near Leiston, Suffolk.
The blaze in a building which is used to control fuel started at 8.45pm on Friday and was not fully extinguished until 3.40am yesterday.
Crews wearing breathing equipment entered a charcoal absorber used to filter gas and flooded it with water to cool the surrounding area.
Anti-nuclear campaigner Charles Barnett of the Shut Down Sizewell Campaign said: 'This fire is regrettable and very worrying.
'Making electricity from nuclear power is a highly-dangerous process.
'I want to find out what went wrong here.'
The station has been closed since March for repairs to failed heaters which caused moisture levels to rise in the station's containment building.
British Energy hopes to have the station operating again by September. The stoppage is thought to have cost the firm millions of pounds in lost electricity production.
British Energy, the station operator, insisted that the fire was 'small' and had not been a danger to anyone.
Sizewell B station director Jim Crawford said: 'The fire has been safely extinguished and the emergency services have left site.
'We would like to thank all those involved for their swift response.
'At no time was there any risk to the public and all staff were safely accounted for and nobody has been hurt.
'Our community liaison officer has proactively been in touch with our contacts in the community to reassure them that the incident was safely managed in line with our well rehearsed emergency plans.'
As engineers remained on-site, a British Energy spokesman said the cause of the fire had still not been established and a full investigation was taking place.
He added: 'The event has been provisionally categorized at level 0 on International Nuclear Event Scale which means of 'no safety significance'.'
Suffolk Fire Service initially sent three fire crews to help power station-based firefighters.
A senior fire officer later called out another three fire appliances and two control vehicles.
Ambulance paramedics attended as a precaution, but nobody was injured and no steps were taken to evacuate nearby residents.