One person has died and several others were critically injured after a minibus, believed to have been carrying senior citizens, overturned on a motorway near Wollongong, police say.
All northbound lanes of the M1 motorway have been closed at Yallah, about 20 kilometres south of Wollongong, following the crash between the bus and a truck just before midday on Wednesday.
The bus, which is registered to an aged-care facility, came to rest on its side, with its roof severely damaged.
A NSW Ambulance spokeswoman said paramedics were called to the motorway to reports that senior citizens on a bus had been injured.
The spokeswoman said paramedics treated nine people - eight people from the bus, and one person who was believed to have been in another vehicle.
Three patients were initially listed as critical, although police later said one of those people - a woman who was a passenger on the bus - had died.
One other person was listed as being in a serious condition, while the remaining patients suffered injuries that were not considered life-threatening, the NSW Ambulance spokeswoman said.
The circumstances of how the bus and the truck collided are under investigation.
The two drivers were not injured, and have been taken to hospital for mandatory tests, police said.
The northbound lanes of the M1 are expected to be closed for some time while crash investigators examine the scene.
All northbound vehicles are being diverted on to New Lake Entrance Road and Windang Road, through Shellharbour and Windang.
Light vehicles already in the traffic queue are being diverted onto Yallah Road and Marshall Mount Road to rejoin the M1.