A person who was critically injured in a crash on State Highway 3 three weeks ago has died in hospital today.

They are the second person to die as a result of the crash, which involved a car and a truck at the intersection of Rangitikei Line and Oroua Road near Palmerston North at 7.30pm on January 9.

Police have not released the person's gender, name or age but said their "thoughts are with their families and loved ones".