There are two confirmed cases of COVID-19 aboard the Sofrana Surville cargo ship off Queensland's Sunshine Coast.
The New Zealand Ministry of Health said on Thursday the two positive cases could be the source of the port worker who tested positive on Saturday.
The Sofrana Surville had travelled from Papua New Guinea to the Solomon Islands to Brisbane to Tauranga to Auckland.
The New Zealand port worker was on board the cargo ship on October 12 and 13 conducting maintenance work while wearing personal protective equipment.
All 19 crew members were tested on Wednesday and three show evidence of a current or previous COVID-19 infection.
One person returned a negative PCR test and a positive serology test, indicating they have previously been infected with COVID-19 but have now recovered.
Another person returned a weak positive PCR test and a positive serology test.
The third person returned a positive test with results indicating a mid-late current infection.
Australian authorities will be carrying out a genome sequencing test on the positive cases to help determine whether the infected crew members are the actual source of the port workers infection.
The two new cases will not be counted in Queensland's tally until they arrive on the mainland.
