An 11-year-old boy has died after a car carrying seven young people hit a tree in Ngaruawahia.

The seven occupants, who were all aged 15 and younger, were taken to Waikato Hospital after the car crashed shortly after 6pm last night.

They had injuries ranging from serious to critical, and one remains in a critical condition.

All six survivors remain in hospital, and many of them are understood to be related - either as siblings or cousins.

Detective Senior Sergeant Stephen Ambler says it's a tragedy for the community, as the children are all local to the area.

Police are investigating the incident and are seeking witnesses who have seen the white Toyota Wish vehicle involved.