DETECTIVES believe a shopper may be unwittingly holding the key to catching an armed robber who has struck six times.

A large-scale hunt was continuing in Blackburn today for the raider, who has left a string of shop assistants terrified after pointing a gun at their heads.

But officers believe a witness who has not yet come forward may have vital information.

The latest raids happened on Sunday at Bargain Booze in Livesey Branch Road and Booze Buster in Wensley Fold shops that he had held up the previous week.

Previous robberies happened at Victoria Wine, Redlam, in March, and the Carol Bookmakers in Dyson Street in April.

In all raids, shop assistants have been threatened and told to put cash and sometimes tobacco in a bag.

Yesterday David Parsons, a director of Bargain Booze, branded the robber "inhuman" after telling how his staff had been left traumatised by the incidents.

And he also put a £1,000 reward up for information leading to the conviction of the robber.

Today, Det Sgt Paul Ryan, of Blackburn CID, said a large number of officers were following up leads in the hunt for the robber.

Det Sgt Ryan added: "We are asking members of the public to look clearly at the times, dates and locations of the incidents and think if they were in the area or in these premises around the times.

"It maybe they know something which they think do not think is relevant, but could be very relevant to us."

Det Insp Paul Withers, head of Blackburn CID, has confirmed the force has brought in extra resources to help catch the robber.

Call Blackburn police on 01254 51212 or Crimestoppers on 0800 555 111 with information.