A police statement said the southbound lane of Athol Five Rivers Highway (SH6) was closed near Five Rivers Cafe, south of Athol following the crash, suspected to be due to black ice.
Emergency services attended and four people were taken to hospital following the crash, one serious, two moderate and one minor.
A Hato Hone St John spokesperson said a total of 12 people were assessed at the scene.
The eight not taken to hospital only suffered minor injuries and did not require further treatment.
The bus was part of a Chinese tour group heading from Queenstown to Milford Sound, police said.
Police have asked drivers to avoid the area and take alternative routes if possible.
Drivers have also been asked to take extra care on the roads due to black ice.
NZTA said there was stop/go management in place and a temporary 30kmh speed limit in place.
