Local police said that there was "no nuclear risk" and two people were sent to hospital after suffering suspected smoke inhalation, Xinhua reported.

Images circulating on social media showed large flames and thick smoke coming from a tall white building, purportedly at the shipyard.

Emergency services were called at about 0044 GMT to the site, located in the coast city of Barrow-in-Furness, where Britain's nuclear submarines are built.

Local residents are being advised to remain inside with their doors and windows closed while the incident is ongoing, said police.

The craft that have been built here include the four Vanguard Class submarines that make up Britain's Trident nuclear programme, according to BBC.

Four new nuclear submarines from the Dreadnought Class and the last of the Royal Navy's seven new nuclear-powered submarines, part of the Astute Class, are also being built at the site.