One person has died and a number of others were injured following a crash which involved a bus, a police vehicle and another vehicle on State Highway 1 at Warkworth, north of Auckland.

Police said shortly before the crash which happened about 6.30pm staff in the patrol vehicle saw a vehicle travelling at speed on State Highway 1.

"Our initial information is that they signalled for it to stop, at which point it has veered suddenly and collided with the bus," Waitematā District Commander Superintendent Naila Hassan said in a statement.

The driver of the vehicle died, an officer and a person in the bus sustained moderate injuries, she said.

A number of other people in the bus which was carrying about 40 passengers are reported to have minor injuries.

The Serious Crash Unit is examining the scene to establish what happened and the Independent Police Conduct Authority has been informed.

Waka Kotahi said State Highway 1 remains closed between Woodcocks and McKinney roads due to the crash and is likely to remain so for most of the night but a detour is in place.