Police are investigating a robbery at the Z petrol station in Tinwald, Ashburton on Thursday 23 August.
The offender entered the petrol station around 7pm armed with a large knife.
The sole attendant was able to lock herself in an office as she saw the offender entering the station.
The offender jumped over the counter and attempted to open the till.
When that was unsuccessful he removed the till and fled on foot around the south side of the building.
Police would like to hear from anyone who saw the offender (pictured) in the area or anyone who has information which could assist our investigation.
If you can help, please call Ashburton Police on 03 307 8400, quoting file number 180823/5291 .
Information can also be provided anonymously via Crimestoppers on 0800 555 111.