A rescue helicopter was dispatched, but conditions were too cloudy for it to land, and a search and rescue team was sent in on foot from near Ketetahi Hut.
It was a two and a half hour walk to Oturere Hut, and during that time the two other trampers who had already arrived at the hut made contact by texting, Shepherd said.
All four trampers were reunited shortly before midnight, after the pair in the hut went back out to find their friends, he said.
One of the group was so cold the other three had to carry her back to the hut around 2.30am.
The SAR team arrived at 2.45am to find one of the trampers hypothermic, Shepherd said.
The rescuers then stayed at the hut overnight with the four friends.
Earlier this morning, a helicopter was dispatched to pick up the SAR volunteers and the trampers, Shepherd said.
The group of four became separated in poor visability and darkness, a statement from the Greenlea Rescue Helicopter - which was sent out to help with the rescue - said.
"Due to the weather conditions on some of the slopes of the mountain, the helicopter was not able to conduct a full search of the area. However we were able to position search teams as high as possible on the mountain, below the cloud base."
Rescuers were able to cover ground"at an astonishing pace", the statement said, because of information gathered via text messages and broken phone calls with the group.
The missing party was found around 1 kilometre from the hut. One pair was "rapidly succumbing to the cold was unable to walk".
"This person needed to be carried to the hut by rescuers, where they had no choice but to stay the night."
The statement added: "There is no question that if they had not been found they would have perished in the conditions overnight."
The Greenlea Rescue helicopter returned to the Oturere Hutt this morning to retrieve the "very cold" hikers and LAND SAR and alpine rescue volunteers.