Anyone who was in the area during or after the four-vehicle smash is urged to contact police.
Police say anyone who saw four vehicles of interest in the area before the crash might be able to help in the investigation.
Anyone who saw these vehicles in the area before the afternoon crash has been also asked to contact police:
• An orange 2014 Ford Ranger ute, registration MHL704, towing a trailer.
• A grey 2013 Toyota RAV4 station wagon, registration HDW704
• A blue 2007 Mazda Atenza, registration LBF327
• A blue 2019 Mazda2, registration MPF649.
Three ambulances, two helicopters and a manager attended the accident scene, along with Fire and Emergency New Zealand and police staff.
Anyone with information should call 105 and quote file number 200903/1062.
Alternatively, information can be provided anonymously to Crimestoppers on 0800 555 111.