A central Dunedin street has been closed after several ice-related crashes this morning.
A police spokeswoman said four cars crashed in Heriot Row between London and Constitution St from 8.20am.
"The road is slippery and cars are sliding down the hill on the frost. The drivers of the four cars have no injuries.''
Three of the four vehicles could be drivable but police advised them to wait, she said.
Police blocked Heriot Row to stop more vehicles crashing.
The Dunedin City Council this morning advised of treacherous conditions because of widespread frost, and urged motorists to take extreme care.
Inland, the Queenstown Lakes District Council says ice and grit have been reported the length of SH6 from Wanaka through the Kawarau Gorge, past Frankton to Kingston.
There is also ice and grit on the Crown Range, particularly the Wanaka side. The Central Otago District Council advises that all roads are open except for Danseys Pass, but ice and grit are widespread in the region.
MetService shows a cold start in the south. Dunedin Airport recorded a temperature of -4C at 7.30am. The city is expected to get a mainly fine day with northeasterlies developing in the afternoon.
Police said the explosive - believed to be an old grenade - has been taken away.