PORTSMOUTH, Va. (WVEC) -- An employee at Norfolk Naval Shipyard was injured Tuesday morning while working on the USS San Francisco (SSN 711) submarine.

A shipyard spokesperson said the accident happened around 9 a.m.

Colleen Sheehy, an assistant shift test engineer at Norfolk Naval Shipyard, was taken to Sentara Norfolk General Hospital.

Sheehy was injured while transiting a hatch aboard USS San Francisco (SSN 711). Sheehy remains in critical condition.

The cause of the injury is being investigated.

The San Francisco, a Los Angeles-class nuclear submarine, is currently being converted to a moored training ship and has been at the shipyard since January 2017.