FIRE broke out on board a nuclear-powered submarine as 20 people were working on it.
The blaze occurred in the conning tower of HMS Astute, which is being built by BAE Systems in Barrow, Cumbria.
The workers were evacuated while the fire was put out by Cumbria Fire Service on Saturday afternoon.
The full extent of the damage is still being assessed.
Neither the submarine’s nuclear reactor nor its diesel engines were operating at the time of the blaze.
BAE spokesman Chris Nelson said: “The initial investigation is that the damage is limited to the exterior of the submarine at the top of the bridge fin.
“A full damage assessment is now under way.
“We are not willing to speculate on the cause of the fire.”
The £1.2bn submarine is due to turn on and test its reactor, then be delivered to the Royal Navy for sea trial, later this year.
