Jacinda Ardern talks to the media after NZ's third coronavirus case was confirmed.

New Zealand's third coronavirus case is an employee of an Auckland steel company and his father is also being tested, health officials have confirmed.

It's thought the older man, who had travelled to Iran, may have passed on the illness to his son and he's being considered a "probable" case even if his test results are negative.

All four of the country's confirmed cases of the virus are based in Auckland.

KENNY RODGER An employee at south Auckland's Glenbrook Steel Mill has been diagnosed with Covid-19. (Pictured in 2001).

They include a person who travelled from Iran, a mother in her 30s who travelled from Italy, her husband, and the first locally-transmitted case – the man in his 40s who works for NZ steel - whose family recently travelled from Iran.



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Health officials confirmed this on Friday morning.

In a letter supplied to Stuff, New Zealand Steel, which owns Glenbrook Steel Mill in south Auckland's Waiuku, said it was advised one of its employees had tested positive for Covid-19 on Thursday morning.

"We are pleased to advise that the affected employee has confirmed that they are not seriously ill and are in isolation at home," chief executive Gretta Stephens said in the letter.

It said the company was working directly with the Ministry of Health, and the practices it had put in place were consistent with the ministry's recommendations.

Stephens said NZ Steel would be contacting and working with employees that had primary contact with the person diagnosed with the virus.

"On advice from the Ministry of Health, primary contact is currently defined as direct face to face contact for more than 15 minutes or working in close proximity in a confined area for more than 2 hours."

Stephens said she could confirm the employee had not been in any plant operating areas or the cafeteria, the letter said.

Staff were advised that if they were feeling unwell, they should speak to their supervisor/manager in the first instance.

MONIQUE FORD/STUFF New Zealand Steel employees have been encouraged to thoroughly wash and dry their hands regularly to minimise risk of getting sick.

Ministry of Health director-general of health Dr Ashley Bloomfield said close contacts of the NZ Steel employee have been contacted.

His father, who is suspected to have transmitted the disease from Iran, is still being tested.

Symptomatic family members will be tested, and those without symptoms will be offered testing, he said.

There have been 217 negative tests and four positive tests of the virus in New Zealand so far.