Detectives probing two attacks on bookmakers in Halifax are working with police in Bradford after similar incidents there.
A gang of robbers armed with machetes hit Ladbrokes in Ovenden Road in Ovenden, Halifax on Thursday, August 16.
Detectives revealed last week they were linking the theft to an attempted robbery at William Hill bookmakers in Keighley Road, Ovenden, the Saturday before.
Now police say they are working with police looking into similar thefts at bookmakers in Bradford.
Officers there have arrested three men on suspicion of robbery.
Anyone with information that might help police should call Calderdale CID via 101 or Crimestoppers on 0800 555111.