The Criminal Investigation Branch was investigating the robbery, Acting Detective Sergeant Simon Keith said.
Police would examine the scene today and they, along with Victim Support, were working with the injured staff members.
Keith said police wanted to hear from anyone who might have information about the robbery or might have seen any suspicious activity in the area.
Police also urged anyone who finds discarded clothes in Bishopdale or Harewood to contact them immediately.
They asked anyone who can help to call Christchurch Police on 03 373 6400 or anonymously contact Crimestoppers on 0800 555 111.
- Additional reporting: NZ Herald