Police have been investigating a double fatal crash north of Timaru and have been seeking help from the public.

Emergency services were called to the crash involving a car and a truck on State Highway 1 near Brosnan Road about 5.10pm yesterday. Two people died at the scene and another person was airlifted to hospital in serious condition.

Police said enquiries have been continuing and officers have been asking for any information which may assist. The white truck was travelling south and the silver station wagon was travelling north.

Police said there was a separate crash before the fatal crash involving other vehicles about 500 metres north of the scene on State Highway 1 which caused traffic to back up. Officers have been seeking information from anyone who witnessed this crash as well.

Anyone who saw what happened or who has information which may help has been asked to contact Police via 105 and reference file number 251120 or 2692.