Police were first called about 6am on Sunday to disperse about 30 party-goers from the upstairs flat in Itchen St.
Sergeant Tony Woodbridge, of Oamaru, said the party, at which DJs were playing, was quiet early on, but later a fight broke out between up to 10 people.
Four people were removed from flat by the party's organisers, but as they left the building they broke windows of a downstairs business, causing about $1000 damage.
Police arrived to find vomit against the walls of the flat and on the footpath and reports of fence pickets being used in the fighting, Sgt Woodbridge said.
A 23-year-old man involved in the fighting received stitches around his mouth.
Police were called to the building again at 8am to find music still blaring and people lingering.
The party might also be connected to a burglary at the St Vincent de Paul Opportunity Shop on Tees St about 6am on Sunday, Sgt Woodbridge said.
Someone forced entry to the store and some stolen property was found inside the party flat.
He said police were also looking at whether or not an illegal bar was running during the party. If police found there was an illegal bar they would consider prosecution.
No arrests had been made by yesterday, but police were talking to those involved.
``We are aware that there were people from Christchurch and Dunedin at this party.''
Sgt Woodbridge said the address was known to police with regards to noise and people drinking in vehicles parked nearby.
Officers were working with the property's landlord to help prevent further incidents.
No-one from the flat was at the premises when the Otago Daily Times visited yesterday and the owner of the shop below declined to comment.
The council said it had not received any noise complaints about the weekend's party at that address.
St Vincent de Paul Opportunity Shop manager Jeanette Verheyen said the drawer from the store's cash register was taken and someone had tried to break into the office.
