They are looking into whether biosecurity laws have been broken when Ruby Princess guests were allowed to get off the vessel in Sydney with flu-like symptoms.

Since then, more than 600 people have tested positive for Covid-19 and 10 people have died, the BBC said. 

Ruby Princess remains docked off the coast with nearly 200 unwell crew members onboard.

At a press conference, New South Wales police commissioner Mick Fuller revealed a criminal investigation has been launched. 

“The only way I can get to the bottom of whether our national biosecurity laws and our state laws were broken is through a criminal investigation,” he said.

The BBC reported police had been told by Carnival Australia that there were no coronavirus cases onboard before the passengers disembarked but an emergency medical call had been made the day before. 

A Carnival Australia spokesman said: “We have seen the Police Commissioner’s announcement.

“In addition to willingly participating in the investigation, Carnival Australia will vigorously respond to any allegations of which there must now be full disclosure and the basis for them.”