Police say a woman assaulted with an axe was injured during a brawl in a Hamilton park.
Detective Nick Rolley says it is believed that 15 to 20 people were involved in the fight early on Friday.
"One side has found themselves outnumbered and sought to even the odds, as it were, by arming themselves with various weapons and then returning to the fray.
"The net result of that was a large number of people of various states of intoxication fighting."
Mr Rolley says other weapons included a spade and a bat or stick.
The injured woman is in a stable condition and is likely to be discharged from Waikato Hospital on Saturday.
Police have arrested two men and are talking to other people involved.