Electric Boat, in Groton, is hiring hundreds of employees and putting up new buildings.
Company officials said Electric Boat is doubling production of fast-attack submarines and accelerating design work for a new generation of ballistic missile vessels.
Over the last year, the company has added 270 employees in Groton and an additional 260 at its manufacturing plant in Quonset Point, Rhode Island.
Company officials expect hiring to remain in the low hundreds over each of the next few years. A total of 10,790 people are employed at the two sites.
The company has begun moving workers to the former Pfizer headquarters in New London, a building that it purchased last year with assistance from the state because it was running out of room at the Groton campus.
