An inquiry has begun after a fire broke out at Berkshire's atomic weapons base which maintains warheads for Trident, the UK's nuclear deterrent.
The incident started in a non-nuclear explosives area inside a concrete bunker at Aldermaston's Atomic Weapons Establishment at 2100 BST on Tuesday.
A male worker suffered minor injuries but the company said 14 people living nearby stayed overnight in hotels.
A 600m (650yd) cordon has now been reduced to 300m (328yd), it added.
Local authorities informed
A spokesman for the Atomic Weapons Establishment (AWE) said: "The company has commissioned an independent investigation into the cause of last night's fire and will make all findings available to its independent regulators, the Nuclear Installations Inspectorate.
"We will also be working closely with the HSE [and] we will make our findings public by briefing the AWE Local Liaison Committee which is made up of representatives of local authorities in Hampshire and Berkshire."
He added that the blaze in the "east end of the Aldermaston site was confirmed out at 0110 BST on Wednesday morning" and there were no "radiological implications" as a result of the fire.
The AWE provides and maintains the warheads for the submarine-launched nuclear deterrent.
Crews from AWE's fire and rescue service were called to the scene and were supported by up to 35 local firefighters.
Road closures were in place all morning as a precaution, affecting traffic between the towns of Aldermaston and Padworth Common, but reopened about 1100 BST.
Earlier, Peter Burt, director of the independent Reading-based Nuclear Information Service (NIS), which says it aims to foster debate on nuclear disarmament, said: "This incident shows that accidents can and do happen."
He then called for an independent inquiry into the fire.