FIREFIGHTERS were called to the fourth Astute submarine in Devonshire Dock after a fire alarm was activated.
A crew from Barrow Fire Station raced to the shipyard at lunchtime after a fire alarm on Boat 4 was manually activated.
Workers had spotted vapour coming from a ventilation system on Audacious and were concerned there could be a fire onboard the boat.
The submarine was evacuated but after an investigation it was concluded there was no safety issue and workers were allowed to return to the boat after around an hour.
A spokesman for BAE System said: "An alarm was manually initiated after vapour was noticed coming from a ventilation system on Astute Boat 4 at about 11.15am.
"The boat was evacuated and emergency services were called as a precautionary measure.
"An investigation quickly concluded that there was no safety issue and employees were back at work within an hour."
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