FILE PHOTO: A worker walks between the first two Astute class nuclear submarines as they are built in the Devonshire Dock hall at the BAE systems facility in Barrow-in-Furness, northern England, May 8, 2007. REUTERS/Phil Noble (BRITAIN)/File Photo

LONDON (Reuters) - A shipyard in Barrow-in-Furness, northwest England, that builds Britain’s new generation of nuclear submarines reopened on Wednesday after being briefly evacuated due to an incident, defense company BAE Systems said.

“Following an extensive sweep of the Devonshire Dock Complex (DDC), including the four Astute class submarines in build, nothing suspicious was found,” the company said in a statement.

“We expect to be able to close the incident shortly.”

It did not specify the nature of the incident but an unidentified source told The Mail, a publication based in Barrow-in-Furness, that the evacuation followed a warning about a bomb on one of the Astute-class submarines.

Ambulances and police were called to the shipyard.

Barrow-in-Furness also makes the new generation of four Dreadnought-class ballistic missile submarines that from 2028 onwards will replace the Vanguard class vessels which form the basis of the United Kingdom’s Trident nuclear deterrent.

Dreadnought-class submarines will measure 153 meters long, with a displacement of 17,200 tonnes, and have a PWR3 nuclear reactor.

BAE Systems, Rolls Royce and Babcock are the main industrial partners in the 31-billion pound ($41 billion) Dreadnought project.