(CNN) Sailors from the coronavirus-stricken USS Theodore Roosevelt began returning to the aircraft carrier Wednesday for the first time since they were moved ashore because of Covid-19, the Navy announced in a statement.

According to the Navy, returning sailors can do so after completing a period of isolation or quarantine and testing negative for the virus twice. The first sailors to return to the ship will be those "responsible for critical services on board."

The sailors have been ashore in Guam as part of a massive effort to evacuate all of the ship's nearly 5,000 troops and ensure they are virus-free through testing. These initial returning sailors will replace several hundred who had been left aboard to operate essential functions to keep the ship running, including manning the nuclear plant and providing safety and security.

Those sailors who had remained on the ship as part of the "watch" team will now move ashore in Guam and wait at least 14 days to ensure they test negative for the coronavirus. Once all of that happens, the Navy hopes to send the aircraft carrier back out to sea.

Still unresolved is the fate of the ship's former commanding officer, Capt. Brett Crozier , who was relieved of duty for allegedly violating the chain of command in expressing concern about the crew's health.