ARMED attackers who stabbed to death a Blackburn jeweller and his wife could have been searching for a valuable gem, it was revealed today.

The disclosure came as the family of murdered Mohammed and Bilquis Karim offered a substantial reward in a bid to catch their killers.

Police also revealed that footage from CCTV cameras in the couple's shop was being examined for clues.

The badly mutilated bodies of Mr Karim, 52, and his wife, 48, of Whalley Old Road, Little Harwood, were discovered in a rear room at their shop in Church Street, Preston, on Friday. The team of 50 officers working on the murder inquiry is investigating rumours that the rare diamond may be at the centre of the violent attack.

Acting Det Supt Mike Arnold said: "Rumours that Mr Karim was murdered for a valuable diamond remain just that, rumours.

"He was well known in the jewellery trade, and in the course of business took in items of a specialised nature, but we've not been able to substantiate rumours he was murdered because of a particular diamond in his possession.

"The family have offered a substantial sum to anyone who can offer any details or information which will lead to the capture of the people responsible for this murder." The alarm was raised by the couple's sons, Shabir and his elder brother Shafiq after the couple failed to pick up their four grandchildren from school.

The pair forced their way in to find their parents had been stabbed.

Shabir said: "I still cannot bring myself to talk about it, it has been so bad."

Mr Arnold, who is leading the murder inquiry, said: "It is still not clear what the motive was and we are looking at all possibilities.

"Although there was still a substantial amount of jewellery in the shop this could have been a robbery which went very tragically wrong. "We are also alive to the fact there could have been a racist element and at this moment in time we are not ruling anything out.

Home Office pathologist Paul Johnson has confirmed the cause of death for both victims was multiple stab wounds, although it is still unclear how many people were involved in the attack.

People in the Church Street area of Preston noticed customers visiting the town centre shop throughout the day but police are keen to find out when the murder happened.

The couple used a security system to vet customers before they allowed them into their store but there were no closed circuit television cameras in the shop. Police are also carrying out door to door inquiries in the area in a bid to piece together the events leading up to the killings.

They particularly want to hear from any passengers of buses that passed the shop between 2pm and 5pm on Friday.

Mr Arnold said: "We want to talk to anyone who was in that area.

"We will also be taking a closer look into the couple's business associates and background.

"Anyone with information should ring 01772 618800. We will deal with all calls in the strictest confidence. Mr Arnold was interviewed last night on the BBC Radio Lancashire programme, The Asian Word, which is translated into Urdu, in an attempt to glean information from that section of the community.

He added: "We'd ask people to be patient if they've called in with information and not been spoken to by an officer on the team."

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