A "significant fire" has broken out at the BAE Systems nuclear submarine shipyard in Barrow-in-Furness, police have said.
Emergency services were called to the site, where the UK's nuclear submarines are built, at around 00:44 on Wednesday.
Two people have been taken to hospital after suffering suspected smoke inhalation.
Police said there is "no nuclear risk".
Local residents are being advised to remain indoors with their doors and windows closed while the incident is ongoing.
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