A Hato Hone St John spokeswoman said ambulance officers were called to a house in Hallenstein St about 11pm, where they assessed and treated two patients — one in a critical condition and one in a serious condition.
Both were transported to Lakes District Hospital.
Acting Senior Sergeant Iain Notman described the incident as a "grievous assault" on two people.
He said two men, aged 20 and 37, were taken into custody at the scene without incident.
They were later charged with two counts of wounding with intent to cause grievous bodily harm, and one count of obstructing police.
The two men are due to appear in the Queenstown District Court.
A guard was in place on Saturday while a scene examination took place, he said.
"Police are now working to establish what exactly has occurred, and are making inquiries to identify and locate any further alleged offenders.
"Members of the public may see an increased police presence in the area while this is ongoing."
