Investigators have left the scene of a serious crash on the Gibbston Highway near Arrowtown.

All five occupants of the two vehicles were injured in the head-on crash in the Gibbston Valley, two of them seriously.

Police say the accident happened on State Highway Six at around 12.30, near the Kawarau Bungy Bridge.

They believe a Toyota Corolla Sedan crossed the centre line and collided with a Toyota Corolla hatchback travelling in the opposite direction.