Police investigating a double fatality crash on State Highway One north of Timaru yesterday, want the public's help

Two people died and a third was seriously injured when a station wagon and truck collided near Brosnan Road, just after 5pm.

Police say there was a separate crash, involving other vehicles, about 500 metres north of the scene shortly beforehand, and it caused traffic to backup.

Police would like to hear from anyone who saw the earlier crash.