NSW Police were called to the ship moored off Botany Bay about 6.30pm on Sunday following reports three people needed medical care on board.
One patient was in a critical condition,while the other two were in serious conditions. They were taken to the Royal Prince Alfred Hospital.
"Anyone who has to come off,comes off at my approval,"NSW Police Commissioner Mick Fuller said on Monday morning.
"Three people needed medical attention who are all under healthcare at the moment.
"I can say the federal government has issued notices that any cruise ships in Australian waters need to return to your port of commencement. I am sure that they will make way this morning."
He said the three crew members were not Australians.
Sunday night's extraction was made more challenging as the patients required a boat-to-boat transfer,with one NSW aeromedical doctor and four paramedics in attendance.
A statement from Carnival Australia,the company that represents Princess Cruises,said the three members had been cared for by the medical team on board the Ruby Princess for acute respiratory symptoms.
"We are also actively considering options for the repatriation of crew members from ships that are now out of service with the exception of those crew members required for the safe operation of the ships,"a statement from the company said.
"We are in contact with the Australian government to seek ways to enable crew where possible to go home."
The ship,which docked in Sydney on March 19,has had several reported cases of coronavirus among the 2647 passengers who were allowed to disembark.
On Sunday,189 cases from the ship had been diagnosed and
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