Government veterinary officials are investigating prem-ises near the Queensbury farm forced to slaughter its herd in a bid to track down the route of the foot and mouth infection.

But Ministry of Agriculture, Fisheries and Food officials say the source of West Yorkshire's first case of foot and mouth disease remains a mystery more than a week after it was confirmed.

Despite the culling of 135 cows and 7,000 chickens, farmer Richard Sutcliffe faces six more weeks of cleansing on his land as Government officials continue the process of sterilising the site.

Today animal health officers were continuing their inquiries into the root of the infection which led to the slaughter of the animals at Bobby Green Farm in Queensbury.

There had been claims that the virus had been transported via sheep from Scotland, with a discrepancy in movement certificates leading to the animals being allowed into the country and infecting a nearby abattoir.

Officials from MAFF have not ruled out the possibility that the herds at the Bradford farm were infected in this way.

MAFF Spokesman Graham Woods today said that all premises in the vicinity were being examined.

He said: "We have no idea how long the investigation will take, but we will be exploring the possibility of the abattoir.

"I am sure that we will be looking particularly closely at any holdings or premises within three kilometres of Bobby Green Farm.

"All the farm records will be checked to see where the animals came from and where they have gone.

"All I can say is that all possibilities are being investigated. Whatever outbreak we have gives rise to a detailed and fairly long drawn-out examination to ensure that all possibilities are explored for the source of the infection."

As the pyres burned on, farmer Mr Sutcliffe said his biggest worry had been laid to rest by MAFF officials:

"They told me that we would have known by yesterday if any more connected cases had sprung up in West Yorkshire, and so far there haven't," he said. "Mine was the first case in the county and I hope it will be the last."

The past week has seen the family's fortunes nosedive as foot and mouth led to mass culling with the fires expected to rage on until the weekend and no possibility of restocking for at least six months.

Mr Sutcliffe added: "People will be disinfecting the site for the next 42 days, and then six weeks before we can restock in September they will be back to do it all again.

"All the manure gets cleaned out and then they have to disinfect it again. It's not over by a long way yet.

"I just want to know how it came to my farm and this country."

Meanwhile, a Bradford Council ban barring people from working on 15 allotments in the district has been lifted after advice from MAFF.

The ban was imposed after the foot and mouth outbreak but a spokesman for the Council said: "The allotments in question have now been supplied with disinfectants and allotment holders told they can return to their plots so long as they disinfect their boots."