Two of the nine Covid-19 positive crew on the Mattina container ship who were transferred to hospital for assessment this morning are back on board.
The Southern District Health Board said the pair did not need to be admitted.
The Mattina, which sailed from Indonesia, docked at a quarantine area in Bluff yesterday with nine crew testing positive for the virus.
At a media conference this afternoon, Director-General of Health Dr Ashley Bloomfield said two of the crew were transferred to Southland hospital this morning.
"There is regular ongoing testing of the crew ... it may well be that there are further positive cases," he said.
Bloomfield said genome sequencing was being done.
And in a statement, the Ministry of Health said all Infection Prevention and Control measures were in place, including the appropriate use of PPE.
Officials, including public health, were now assessing whether the rest of the crew will remain aboard throughout their quarantine period.
Results of additional testing will be reported tomorrow, the ministry said.
It said the Southern DHB had plans in place for the appropriate management and treatment of any crew aboard the vessel requiring hospital level care.
"The ministry expects to have further information about the source of those infections when whole genome sequencing is completed in the next few days."