More than tree months after a crash which claimed the lives of two people, police are still appealing for help finding a possible witness.

The two-car crash happened around 8:35am on the Waimate Highway at Glenavy in South Canterbury on Tuesday December 26, 2017.

Horton James Hill, 80, of Christchurch and 31-year-old Matthew James Gilchrist of Oamaru died at the scene of a crash between Carrolls and Stangers Rds.

Police said they had received information from another witness that a female driver of a red car was also at the crash scene, but left before emergency services arrived.

This unknown witness is described as Caucasian, in her mid-50s with shoulder-length dark hair. She was driving a small red Toyota-style car.

Police had made inquiries in the Glenavy area but have not identified this woman as yet. It is possible she lives elsewhere and was travelling through the area at the time.

Police would like to speak with this woman as a possible witness who may be able to help us with information to establish what happened prior to the crash.

Contact Waimate Police on (03) 689 7272 if you can help.