Police are appealing for witnesses as they try to track down the southbound car involved in the crash north of Napier on Monday morning.
The crash happened at about 9.30am near Ellis Wallace Road, Eskdale, when two cars collided in wet conditions.
Police said after initial enquiries it appeared that the southbound vehicle may have lost control and crossed the centreline into the path of the northbound vehicle.
One person was out of the wreckage by the time emergency services arrived but the other two occupants were trapped in the wreckage.
After a prolonged rescue operation the scene was finally cleared and the road was re-opened shortly before 12.30pm.