Police Scotland are investigating a two-vehicle collision that occurred on the A90 Peterhead to Ellon road near to the Toll of Birness, Aberdeenshire, about 6pm on Wednesday, April 5.
The collision involved a white Peugeot 207 and a silver Volkswagen Passat.
The four occupants of the Peugeot and two occupants of the Volkswagen were all conveyed to Aberdeen Royal Infirmary with serious injuries.
Sergeant Peter Henderson of the Road Policing Department said: "Our thoughts at this difficult time are with those involved and their families. An Investigation into the collision is underway.
"In order to help establish what happened, I would urge anyone who may have seen either of the vehicles prior to the collision, or who saw the incident and has not yet come forward, to contact Police on 101 as soon as possible.