Two of today's 25 Covid-19 cases are community transmission from a port worker who previously tested positive for the virus on Saturday.
Both of the cases are workplace contacts of the man.
Dr Ashley Bloomfield outlined how the first workplace contact was a casual contact that works as the same firm and only had a few minutes in the same room as their symptomatic colleague on Friday.
This person returned a positive result yesterday after showing symptoms. They have one household contact who has been tested and is isolating, Bloomfield says.
The second person is another workplace contact who has been at the Jet Park Hotel quarantine facility since Sunday as they were deemed a close contact.
After testing negative on Friday, the person began to show symptoms yesterday and subsequently tested positive.
His household contacts are isolated and have been tested.
These contacts had returned negative results previously but are now considered close contacts.
Bloomfield believes the Sofrana Surville ship is still the source of infection. The original infection had worked at ports in Auckland and Taranaki.
The news comes as a total of 25 new Covid-19 cases were reported today.
Twenty-three of these cases have been caught at the border, leaving the two community cases as reported above.
Yesterday - in cases unrelated to the port worker - 11 Russian and Ukrainian fishermen who flew to New Zealand tested positive for Covid-19, with 14 other potential cases also being investigated.
The Ministry today confirmed that a further 18 of those fisherman had tested positive since yesterday, bringing the total number of Covid-19 cases at the Sudima facility in Christchurch to 29.
The 235 fishermen were brought to New Zealand from Ukraine and Russia as critical workers by Independent Fisheries, Sealord and Maruha Nichiro.
Further to those cases, five other cases were confirmed among recent arrivals today, all of which are in isolation facilities.