At least nine of the 21 crew members on board a containership have tested positive for Covid-19 at a port in the south of New Zealand.

The Marshall Islands-flagged, 4,363-teu Mattina (built 2007) arrived at South Port New Zealand on Sunday evening with two crew members initially testing positive for the virus.

The results of additional tests of the remaining crew came back late Monday evening, confirming a further seven cases of Covid-19 on board the ship.