Dr Fox also attracted attention in the US when it was revealed he treated the Sandy Hook gunman Adam Lanza as a teenager. Lanza later shot dead 26 people in the second-worst school shooting in US history.
He became a fulltime employee in July last year after his time as a locum ended. Health board chief executive Craig Climo yesterday said investigations into Dr Fox were still ongoing.
"We will review the circumstances around Dr Fox's appointment as soon as we can. We don't yet have complete information as key people involved in his registration and employment are on holiday."
It was hoped the investigation would be completed by next week, when Dr Fox is due to return to work. The health board has previously said Dr Fox was fully registered and credentialled to practise in New Zealand and was a "good addition" to the mental health team.
"We have started a review and will complete it as soon as key people involved in his registration and employment return from leave," Mr Climo said.
"As part of our review, we will look into whether there was full disclosure."
The Medical Council of New Zealand has said if it is discovered Dr Fox withheld information it would be treated with "the upmost seriousness". A spokesman yesterday said they were still waiting to speak to Dr Fox.