The managed isolation security guard who went untested between November and April lied to his employer, according to Prime Minister Jacinda Ardern.
Chris Hipkins, the Minister for COVID-19 Response, said during Wednesday's COVID press conference the Grand Millennium managed isolation worker misled his employer, First Security, about being tested.
"The individual concerned was supplying information to their employer that they were being regularly tested - it appears that was not the case," said Hipkins.
While Hipkins shied away from making accusations of "lying", Ardern was more forthright.
"The individual was lying to the employer," she told reporters on Wednesday.
An investigation into how the guard evaded testing for five months is underway but Hipkins says at the moment "the information given to the employer does not match up with the records".
Ardern said it's "ultimately" up to the employer to have measures in place to ensure employees are doing what is required of them.
"If someone is not fulfilling their requirements and lying about it, you can see that it presents issues."
All managed isolation and border workers are required by law to be tested fortnightly, and Ardern says it's up to the employer to decide if the security guard should be sacked for evading the truth.
There is a Government border worker testing register to track who is getting tested - but it's not mandatory.
In a statement on its website, First Security says it is using the national register set up by the Ministry of Health - but Hipkins said on Wednesday it was using a "combination" of their own internal record keeping and the register.
"There is an investigation going on about that - the employer should have been able to verify whether [the security guard] had been tested or not."
He says the Ministry testing register will soon be compulsory
"That will mean that we will then have the complete register so we will be able to have all of that information in a format that's easier to report."
National leader Judith Collins says it is "unfathomable" the guard had not been tested since November.
"The public has been promised for months that all of the frontline border facing staff were being tested regularly. And now to find out [the guard] hasn't been tested for months and he's the staff member who's got COVID? It's just unfathomable."