Raglan Police investigating the cause of a crash in Raglan yesterday, are seeking witnesses to what happened.

Waikato Road Policing Manager Inspector Freda Grace says the crash happened just after 5pm on Wainui Rd, just before the bridge.

'The vehicle, a red utility, was travelling in a westerly direction, when it left the road, crossing the centreline and grass verge before flipping and landing at the bottom of the bank.

"The four occupants of the vehicle all suffered injury. One of the occupants was flown by helicopter to Waikato Hospital, two were taken by road, and one checked at the scene. Police would like to speak to anyone in the area at the time or shortly before the crash who observed anything about the driving behaviour or who saw the crash.

Anyone with any information is asked to contact Senior Constable Smith at the Huntly Police Station on 07 8586200.

As holiday traffic causes congestion at a number of the popular beach locations in the Waikato, drivers are all asked to exercise patience and care, share the road and Drive Social.