The Defence Force says a soldier who collapsed from heat exhaustion is still in an induced coma in Auckland's Middlemore hospital.
Lieutenant Alexander Teira Cowan, 25, was taking part in a selection process for the SAS on Wednesday when he collapsed and fell unconscious towards the end of the activity.
Officials say Lieutenant Cowan received immediate first aid and was rushed to hospital, where he is in an induced coma in intensive care.
The army says he was with a group of other soldiers in the Hunua Ranges near Auckland.
They were required to complete an 8km run dressed in military uniform including boots, and carrying equipment weighing about 10kg.
An inquiry will be carried out.
A spokesperson for the New Zealand Army, Major John Gordon, says that before a candidate undertakes the selection process they normally embark on their own training programme - overseen by Defence Force physical training staff.
"As part of the pre-selection process every candidate is required to undergo a fairly strict medical check and they do ensure that the candidate is at a suitable physical fitness to attend the selection process."
Major Gordon says this is the most severe incident during the process selection they have had in recent times.