Three people have been airlifted to hospital after a tour bus rolled near Te Anau leaving 15 people injured.
Police were called to the incident just after 8am near Mavora Lakes Road.
Te Anau volunteer fire brigade’s chief fire officer, Graeme Moffat, said the bus rolled onto its side.
"I’ll let the police say what the cause of it was but there was a lot of black ice and fog around.”
He understood it was a Korean tour bus on its way to Milford Sound.
St John spokesperson Gerard Campbell confirmed three people were airlifted to Dunedin Hospital, two with serious injuries and one with moderate.
Three rescue helicopters were deployed to the incident.
A further 11 people have been sent to Fiordland Medical Centre with minor injuries.
There were 17 passengers on the bus including the driver and tour guide.
Mr Moffat said three people were trapped only because of their injuries.
"My guys didn’t actually do any cutting as such, they assisted ambulance with those people and helped get them out of the bus.”
The highway was initially closed after the incident but is now open to one lane and expected to be fully open within three hours.
A general warning was issued at 8.45am by the New Zealand Transport Agency (NZTA) which stated black ice was present from Mossburn to Te Anau.
"I don’t think the road is a bad road, the road’s fine, people just need to learn to drive to the conditions really,” Mr Moffat said.
NZTA maintenance contract manager for Southland, Josh Webb, confirmed the area of the crash was gritted at 5am and anti-freezing material was applied within the last two days.