Police said one person has been critically injured and another person seriously injured.
One person has been transported to Auckland City Hospital in a serious condition, Hato Hone St John said.
A person who works nearby to where the crash happened told the Herald they heard a very loud bang, which “sounded like a large shipping container had been dropped on to the road”.
Fire and Emergency New Zealand said two rescue crews and one fire engine responded to the incident on Main Highway.
Crews used rescue equipment to extract people trapped in the vehicles.
Hato Hone St John responded with two ambulances, one manager and one rapid response vehicle.
The police Serious Crash Unit will carry out inquiries at the scene.
Main Highway has been closed between the intersections of Ellerslie-Panmure Highway and Amy St.
Police are asking people to avoid the area if possible and to expect delays because closures are expected for a few hours this evening.
Sign up to Herald Premium Editor’s Picks, delivered straight to your inbox every Friday. Editor-in-Chief Murray Kirkness picks the week’s best features, interviews and investigations. Sign up for Herald Premium here.