The incident happened on Monday, July 23, when a man was challenged by staff as he tried to leave the store with items he had not paid for.
North Yorkshire Police say two other men then became “aggressive and threatening” towards the staff.
The staff members were forced to let the first man go, although the goods he had been carrying were recovered.
Anyone with information is asked to ring North Yorkshire Police on 101 or Crimestoppers anonymously on 0800 555111.