The Maritime Union has renewed calls for crew from foreign ships to be tested before entering New Zealand.
An engineer tested positive for Covid-19 on Saturday - it's suspected he caught the virus on a ship he was working on.
Then yesterday a crew member on another ship which arrived last week returned a weak positive test - indicating he may have had the virus.
Currently sailors flying in to board ships leaving New Zealand don't have to be tested.
The Ministry of Health says it's reviewing measures in place at ports and for ship workers.
The Maritime Union's national secretary, Joe Fleetwood, says they've been calling for extra testing for months - but their concerns have fallen on deaf ears.