Two 18-year-old Nelson men were arrested at the scene.
Police are continuing to piece together the events leading up to the altercation, including carrying out a scene examination, before any charges are laid.
"We will be ascertaining why the altercation started and whether alcohol was involved.
"There were two groups present. One group comprised two 18-year-old men and the other group of four comprised two men and two women," Bruning said.
Police request anyone with information regarding this incident or who may have been near the scene around midnight to contact Nelson police 03 5463840.
Alternatively, information can be passed anonymously to Crimestoppers on 0800
555 111.