Australian health authorities have extended the quarantine period of six people who were on a cruise ship that was hit by an outbreak of hantavirus to late June, local media reported on Thursday.

The cruise passengers will remain quarantined in Perth's suburb of Bullsbrook until June 23, the Australian Broadcasting Corporation reported.

The passengers include four Australian citizens, one permanent resident, and one New Zealand citizen, who arrived at the Center for National Resilience in Bullsbrook on May 15.

Federal Health Minister Mark Butler said the decision to extend their quarantine period was made based on advice from health authorities after another two passengers, from Spain and the Netherlands, tested positive for the deadly infection.

The passengers have been informed of the decision and "remain well," he added.

"They've only been tested again in the last 24 or 36 hours or so and all six have again tested negative," he further said.

Scientists confirmed the outbreak was caused by the rare Andes variant of hantavirus, the only known strain capable of human-to-human transmission, usually through close contact.