Although police are not linking the two incidents, both bookies have been targeted by burglars who managed to get inside the buildings.

The raiders broke into William Hill at Holmeside overnight on Friday, taking a safe and dumping it in a back lane.

Detective Inspector Irwin Smart said the thieves came in through the roof, but police are trying to find out how they managed to get the safe out of the building.

Overnight on Sunday, September 31, Coral's bookmakers at Pennywell shopping centre was raided and a substantial amount of cash stolen from the safe.

The shop was broken into through the fire exit at the back and it is thought the safe was opened using some sort of cutting equipment or explosives.

The store was closed the next day while forensic evidence was gathered, CCTV footage was trawled and telephone and electrical wires, which were thought to have been cut during the raid, were reconnected.

It is believed the break-in took place between 6.20pm on Sunday, September 30, and 8.05am the next day.

At the time a spokesperson for Coral's said burglaries were rare and declined on security reasons to release details on how much cash was taken from the store.

William Hill and Coral's are members of the Association of British Bookmakers, which offers a reward of up to £10,000 for information leading to the conviction of a betting shop raider.

DI Smart added: "We are not making any links between these two at this time."

Anybody with information about the safe stolen from William Hill, which contained an undisclosed amount of money, is asked to contact Sunderland CID, tel: 08456 043 043.