Director-General of Health Dr Ashley Bloomfield says the two connected to the port worker are workplace contacts.

The first case was previously considered a casual contact of the port worker and had a very short exposure to the worker - about three minutes in the same room as them, says Dr Bloomfield.

"The new case became symptomatic yesterday, was tested yesterday and returned a positive result. They have one household contact who is now in self-isolation."

The second case is a previously reported close contact of the port worker. Dr Bloomfield says they were already at the Jet Park quarantine facility since Sunday. They were tested on Friday as part of the routine testing at the port and returned a negative test.

They developed symptoms yesterday, took a test and now returned a positive result, says Dr Bloomfield. "His household contacts were contacts of contacts but were isolated and tested anyway, they are now considered close contacts so will complete the full 14-day self-isolation."

"The ship the original positive case worked on in Auckland, that is now in Brisbane, is still is considered the most likely source of transmission. Tests have been taken but the results are not yet available."

There are 19 crew members on board the ship in Brisbane.

Moving onto the other cases in managed isolation, Dr Bloomfield says there are now a total of 18 cases in the Sudima Hotel in Christchurch that have Covid-19.

The charter flight from Moscow, that stopped over in Singapore, carrying Russian and Ukrainian fishing crew members had tests undertaken before the flight took off. The testing, Dr Bloomfield understands, involved the nasal swab.

Dr Bloomfield says two people weren't allowed on the flight because they tested positive.

A total of 235 fishing crew members are in the Sudima Hotel which is set up just for them.

Some of the 18 cases are new, according to the results of the tests, and some are probably historical, but ongoing testing continues, says Dr Bloomfield.

"The positive cases have now been moved into a dedicated quarantine wing within the Sudima Hotel."

Most of the people were in twin rooms, the close contacts of the 18 cases (those who were in the same room as the positive cases) are now in single rooms and the ministry is working to move all of the fishing crew into single rooms, says Dr Bloomfield.

"All of the staff working at the hotel have been tested over the last three days and additional testing will be provided."

Dr Bloomfield says People at the airport at Christchurch are being asked to be tested, as well as the bus company that transported the fishing crew to the Sudima Hotel.

Yesterday the ministry confirmed that there were 11 cases of Covid-19 at a managed isolation facility in Christchurch, with another 14 possible cases being investigated.

The ministry said it is investigating after the cases were detected during routine day three testing.

None involved cases in the community, it said.

It said the positive cases are part of a group who are the only people staying at the Sudima Hotel in Christchurch.

The cases were on top of the one new imported case that the ministry confirmed as part of its daily update.

With two recoveries in 24 hours, the total number of active cases are 56 and NZ's total confirmed cases till date is 1556.