A husband and wife from Reefton died after their car and a train collided at a level crossing in nearby Inangahua, police say.
The crash happened at Landing Creek Road shortly before 1pm on Wednesday. Serious crash investigators are working to determine the cause. No one else was injured.
A KiwiRail spokesperson said the company's thoughts and sympathy were with the family and such incidents were also distressing for train drivers and other staff.
The crossing has give way signs and no previous collisions have been recorded there, KiwiRail said.
The couple's names will be released when next-of-kin have been told.