Mrs Grace said investigators are still seeking witnesses to the crash who hasn't already been interviewed by police.
She said police expressed their sincere apologies to Ms Andersen's family and the family of Mr Ambler.
Investigators were also still working to establish what caused the crash that killed Mr Ambler, especially "what part, if any, speed, alcohol and not wearing a seatbelt may have played".
His Holden Commodore struck an abutment on a bridge and he was thrown from the car.
Mrs Grace said unanswered questions remained, but it was a timely reminder to send road safety messages.
"We now have two families contemplating empty seats at the family table this Christmas and this is something we want the public to help us prevent other families having to face these holidays."
*Anyone with information about the Karapiro crash is asked to contact Sergeant Warren Shaw at the Te Awamutu Police Station on 07 872 0100.