Four men were in Christchurch Hospital last night with injuries suffered in a bloody street fight in the suburb of Spreydon.
Police were piecing together details and evidence but Detective Senior Sergeant Corrie Parnell said late last night it was still unclear what had happened.
The brawl involved a group of men, thought to be in their early 20s, in Simeon St about 8pm.
Police cordoned a section of the street as shocked neighbours watched.
Parnell said scene examinations would continue today.
He was at Christchurch Hospital checking on the conditions of the people involved and "trying to get my head around what happened".
The four men were in the emergency department with "various injuries", he said.
"I'm unsure how many people were involved, what it's about or what's been the catalyst," he said.
"The investigation is in its infancy."
A man who had recently bought a property in the area said locals had warned him about one residence on the street.
"It's actually a pretty good neighbourhood apart from that crowd," he said.
Police had been at the property the night before, a resident said.
Another neighbour said he could hear yelling and fighting from inside the house, which set dogs barking.
"It sounded like there was a dog fight," he said.
When he went outside he saw about eight people - "there could have been more" - in the middle of the road. The fight was thought to be all but over by then and people were going their separate ways.
A witness described seeing a "blood pool" on the road, which was later covered by police.
Another neighbour said it was not uncommon to hear people "running up and down the street screaming".
"So I didn't think much of it at first."