An army recruit was said to be in a critical condition after nearly drowning in a swimming pool at the Sir John Moore Army Training Regiment barracks, near Littleton, Winchester, on Wednesday.
Private Milton Mahoney (24) was resuscitated beside the pool by an army instructor.
An investigation is now under way.
An army spokesman said: "Every group that should be has been informed, which includes the Military Police and the Health and Safety Executive."
He added that the incident happened during a regular swimming session and that no specialist exercises were being conducted in the pool.
Pte Mahoney was taken to Winchester's Royal Hampshire County Hospital on Wednesday morning and yesterday (Thursday) a spokesman said his condition remained critical.
The army said Pte Mahoney, who only joined up in December, is not a UK passport-holder.
It is withholding details of his nationality until members of his family have been contacted.
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