A probe has been launched into two robberies at Betfred outlets on the same road within a few hours of each other.
A masked robber wearing a balaclava and goggles is said to have burst into a Betfred store on Blackpool Road, Preston, at 8.21pm on Monday, when there were no customers in the shop.
After wedging the door open with a can, he threw a carrier bag at staff, and demanded cash.
He then demanded money from the safe but fled the scene when defiant staff refused.
It happened less than 12 hours after the Betfred shop further up Blackpool Road, at Lane Ends, was robbed at knifepoint.
Detectives say the incidents may be linked.
Det Sgt John Crichton, of Preston CID, said: “The robber in the latest offence wore a balaclava and either goggles or sunglasses, with black or grey trousers and black trainers.
“We are appealing to anyone with information to contact us.”
An investigation is continuing into an earlier incident at 9.30am when a raider threatened staff at the bookmakers with a knife before stealing cash and fleeing the scene.
He is described as having a Liverpudlian accent and could have been with another man.
Witnesses call 101.