An inquiry is under way into how two American submarine crew members fell overboard in UK waters and later died.
The nuclear-powered submarine is based at Norfolk, Virginia
They were among four crewmen who were working in poor weather on the outside casing of the USS Minneapolis-St Paul in Plymouth Sound, Devon, on Friday.
The men were taken to hospital, where two of them were pronounced dead.
Witnesses are being questioned in a joint inquiry by Devon and Cornwall Police, the United States Navy and the Ministry of Defence (MoD).
The nuclear-powered submarine was leaving Plymouth's Devonport naval base at the time of the incident after a week's stay.
Coastguards said the four sailors were tied to the 110m (362ft) vessel and were being "battered about" by the weather.
A rescue helicopter from RNAS Culdrose, a tug boat and a lifeboat were sent to their aid.
The men were taken to Derriford hospital in Plymouth, where two servicemen were pronounced dead.
The servicemen are not expected to be named by the US Navy until after the next-of-kin have been informed.
The two other men were treated for minor injuries and transferred to the sick bay at the HMS Drake, where they are recovering.
A US Navy spokesman confirmed four sailors from the vessel had fallen overboard as it was getting under way from Devonport naval base.
In a statement, they said: "Our thoughts and sympathies are first and foremost with the families and loved ones of the sailors who sadly lost their lives today in this incident."
The MoD expressed its sympathies to the families of the dead servicemen.
The Virginia-based submarine has been operating under the US Sixth Fleet since October and has now continued on its journey.
It has a complement of 137 officers and enlisted crew and can reach speeds exceeding 25 knots (29mph). Its weapons include torpedoes and Tomahawk cruise missiles.