Hundreds of racehorses in Ireland and Britain this weekend could face automatic disqualification following last night's news that nine horses have tested positive for morphine.

The prohibited substance is believed to be in a feedstuff, and samples from up to 20 horses are currently being examined by the Turf Club and the Jockey Club. So far two of the nine horses tested positive are trained in Ireland.

The Turf Club chief executive said that "nothing sinister" is suspected in the contamination of the feed, but if a winner is tested positive, it will be disqualified.

"Under our rules they would have to go," Denis Egan said last night. He also confirmed that the first and second in every race in Ireland this weekend will be tested for the drug.

"There is nothing sinister as far as we can tell," Egan added. "The samples are coming from all over the place. Seed tests are ongoing to find the source of the problem. We have an idea the problem could lie with one particular feed company."

Concerns first arose last week, but the first test results this week have put racing bodies on both sides of the Irish Sea on high alert.

All the winners at Thurles on Thursday were tested with one outcome described as "suspicious".

Up to now nine horses have failed the A-test, and secondary results are awaited on the others. Egan also said any automatic disqualification if the substance is found could end up as a matter for the Turf Club's Appeals and Referrals Committee.

In the meantime, however, the sport is set to be in a state of flux until the problem can be traced.