More than a dozen sailors aboard USS Theodore Roosevelt have tested positive for coronavirus, including some for a second time, a US Navy official has said.
All 13 had previously tested positive for COVID-19 and underwent at least two weeks of isolation.
Before they were allowed to return, affected sailors had to test negative for the virus in two consecutive tests, at least a day or two apart.
The US Navy official said eight sailors tested positive on Saturday, while five tested positive again on Friday.
The tests' accuracy has been brought into question, over a possibility that infection could be at such a low level, it is not detected, which could mean there may have been no relapses.
The coronavirus outbreak aboard the ship was found in March, and more than 4,000 of the 4,800 crew members were sent ashore for quarantine or isolation.
In April, a sailor who was serving on board died of complications related to COVID-19, the US Navy had said.
The sailor tested positive for coronavirus on 30 March and was taken off the ship and put into "isolation housing" along with four other crew members in Guam.
He was found unresponsive on 9 April and died on 13 April.
The aircraft carrier gained international attention after it docked in the Western Pacific island of Guam at the end of March as the number of coronavirus cases on board the vessel rose.
Captain Brett Crozier was "relieved of command" after Navy leaders said he created a panic.
A leaked letter of his called on the Navy to urgently stop the spread of the virus on board.
Acting US Navy Secretary Thomas Modly said in a press conference that Capt Crozier had "demonstrated extremely poor judgement".
He said Captain Crozier had copied too many people into the memo and that he should have gone directly to his immediate commanders who were already helping.
Mr Modly said the memo was sent over "non-secure unclassified email" and "outside the chain of command".
Mr Modly later resigned after criticism in relation to his handling of the situation.
Earlier this month, hundreds of the vessel’s sailors began returning to the ship, in phases, to set sail again.
The repeated positive results have now raised questions over reintegrating troops into the US military if a second infection were possible.
Cover image: USS Theodore Roosevelt (Picture: US Department of Defense).