People vomiting over a balcony and level 2 breaches are among a raft of issues at 90-person knees-up at a Dunedin bar that police are investigating.

Officers were called to Dive, formerly known as The Cook, at 11.30pm on Friday after reports of people smoking cannabis and flicking cigarette butts into a cardboard rubbish bin.

Acting Senior Sergeant Anthony Bond said police did not locate cannabis when they arrived at the scene, but were told people had been vomiting over the balcony.

There were also breaches of alert level 2 Covid restrictions. The 90 people present were not seated and there was no table service.

Bar staff stated they did not have to follow those rules due to it being a private function, he said.

The security guard presented an expired licence, and there was confusion around who the duty manager was - the person whose name was on the duty manager board said the person behind the bar was actually in charge.

''This will be followed up by the alcohol harm team," Bond said.

Dive operator Mike McLeod said as far as he was aware, police had no issues with behaviour at the event, which was a 21st party.

He said they had researched the alert level rules and did not believe restrictions such as being seated or providing table service applied at private functions.

According to the government's Covid-19 website, social gatherings under level 2 are limited to 100 people and physical distancing should be maintained where possible.

McLeod was not aware of anyone vomiting over the balcony.

"They were really quite well behaved.''

As for the security guard, McLeod believed he was fully licenced and was not aware of the licence being expired.

"As far as I'm aware, the police had no issues.''