Top cop 'relieved' Ruby Princess has left

The cruise liner - which has been linked to 21 coronavirus deaths and 600 infections across Australia - is heading up the coast bound for the Philippines after departing Port Kembla on Thursday.

"I am relieved to see it go - it was a large-scale police operation," NSW Police Commissioner Mick Fuller told reporters on Friday.

"The ship left with a lower risk, not a zero risk."

Half the crew was taken off the ship before it left for Manila.

Some 567 crew members were repatriated or taken ashore for treatment by NSW Health with 40 remaining in hospital with COVID-19, Mr Fuller said.

When the Ruby Princess departed on Thursday evening no one on board was positive for coronavirus, but NSW Health will maintain contact with the ship while it's in Australian waters.

There are doctors, nurses and "high-quality medical care" on the ship, Mr Fuller said, and if an emergency extraction is required Queensland authorities will assist.

NSW Police are conducting a criminal probe alongside an independent special commission of inquiry which is expected to deliver its findings to the state government by September.

Mr Fuller said homicide detectives returned to the ship on Thursday to seize additional evidence following the inquiry's hearings this week.

They seized a number of mobile phones "that may have been used in between key players on the ship and people within NSW - particularly around potential health information that may or may not have been exchanged".

The commissioner said detectives were looking for evidence "outside" the health reports submitted by the ship or the triple-zero calls made to NSW authorities.

Police last week gathered a thousand medical files from the Ruby Princess and took a number of statements from those on board.

Australian Associated Press