Wheel victim a recent arrival

The young man who died after the bus he was travelling in was hit by a runaway truck wheel may have only been in New Zealand for a month.

Lam Xuan Hu, a 24-year-old Vietnamese student, died in Auckland Hospital on Friday.

He was seriously injured when two wheels came off a truck travelling on the Southern Motorway on Thursday.

One of the 80kg wheels flew across the motorway median barrier and through the windscreen of a Waka Pacific bus, travelling in the opposite direction.

Hu was sitting in a front seat near the driver, and suffered severe head injuries.

He was taken to Auckland Hospital and police said on Friday his life support machine would be turned off once family members had gathered.

Vietnamese Friendship Association president Nguyen Dang said he understood Hu had only been in New Zealand a short time.

He was hoping to contact his family to offer support.

A spokeswoman for Waka Pacific said they were "immensely saddened" to hear Hu died on Friday night.

"This is a tragic accident and our hearts go out to his family and friends at this time."

The driver of the bus, who was shaken but unhurt, was off duty and receiving counselling.

The spokeswoman said they were trying to contact three other passengers who received minor injuries in the incident, but had not been given details about them.

One was briefly admitted to Middlemore Hospital but was released the same day.

Other passengers reported being showered with broken glass in the incident, about 7.40am on Thursday.

The express bus was only a few kilometres into the journey from Manukau to Britomart when it collided with the wheel between Otahuhu and Mt Wellington.

Waka Pacific staff had not been in contact with the dead man's family, but were hoping to speak to them this week.

Mechanical experts have inspected the truck but sergeant Stu Kearns said the investigation into the incident was ongoing.

He understood the man's father was too ill to travel from Vietnam.

"They're in a state of shock," he said.