Castle St cops run out of pepper spray

Police ran out of pepper spray trying to subdue a drunken mob on a second night of disorder in Dunedin following the arrival of the annual Undie 500 car rally in the city on Friday.

Again facing off against a mob of about 600 people in North Dunedin's Castle St area, police in riot gear used pepper spray to subdue and disperse the hordes. Students again lit fires and pelted police with bottles.

The crowd advanced on officers, "challenging the police line", after police officers tried to grab a man, Inspector Dave Campbell said.

"Many students were pepper sprayed and officers had to call for more supplies as some had emptied their canisters on those students," Mr Campbell said.

Police arrested between 50 and 60 people. This follows the 20 arrests made on Friday night. The weekend's violence and disorder saw the highest number of arrests in recent years.

The annual Undie 500 event, organised by Canterbury University engineering students, involves a pub crawl from Christchurch to Dunedin, in cars worth under $500.

The event has previously caused headaches for Dunedin police left to control riotous behaviour at the end of the trip.

Last year's official Undie 500 was cancelled after rioting in the city resulted in 69 arrests the previous year.

However, an unofficial version of the event still ran and 30 arrests were made after another round of disorder.

Those arrested would be charged with breaching the temporary liquor ban, disorderly behaviour, obstruction and wilfully setting fire to property, and would appear in Dunedin District Court at the end of the week, Mr Campbell said.

Despite promises of better behaviour from students, "nothing has changed".

"The event has once again shown that when large numbers of young adults gather and drink to excess mass disorder is inevitable."