Hopes of a return of racing on Wednesday after a six-day shutdown caused by an outbreak of Equine Influenza took a blow this evening when it emerged that four samples from a Newmarket yard had tested positive.
The infected horses are from the yard of flat trainer Simon Crisford, who for a long time was Godolphin's racing manager before starting training.
The news takes the total number of positives in racing to 10 so far, while there are known to be more involving non-racing horses.
It had looked likely that the BHA would be satisfied that no cross-contamination was caused by infected Donald McCain-trained Raise A Spark running at Ayr last week, and would make a welcome announcement on the resumption of action.
Indeed, after thousands of swabs from across the country had come back negative, signs had looked 'encouraging' that an announcement about a restart could be made on Monday night, according to David Sykes, the BHA's Director of Equine Health & Welfare.
Yet, it was announced late tonight that four horses at Crisford's yard in Newmarket had tested positive, which could spell further delays and yard lockdowns.
A BHA statement said: 'The horseracing community in Newmarket is tonight being informed that four positive tests for equine influenza have been returned this evening in vaccinated thoroughbreds at the yard of a licensed flat trainer in Newmarket.
'The affected yard is that of Simon Crisford, who has been named in order to ensure that the Newmarket community is aware of the yard at which an infection has been identified.
'No non-urgent journeys should be made to this yard - including by the media - and anyone who wishes to travel to the yard is advised to first contact the trainer's office.
'This yard is one of the 174 which has been required to undergo testing due to the fact that runners from the stable competed at the fixture at Newcastle on 5 February, which had been identified as a potential risk fixture. At the moment the affected horses are all contained within this yard.'
The BHA added that a further update would be issued early on Monday, including details of action that is being taken off the back of the incident and the decision tonight regarding whether it is possible to resume racing.
One possible outcome of this development is that the BHA, which is being guided by its industry veterinary committee, could order for some re-testing of horses before allowing racing to resume.
Given the extent of testing that has been required in the effort to contain the outbreak, any announcement today would have come before the analysis of all the swabs had been completed.
It is thought that by last night 1,500 test results had been analysed, with thousands more still to be done.
However, the news of more positive tests does not definitely mean that racing will not resume on Wednesday.
If the BHA is satisfied that none of the stables that had runners at Ayr last Wednesday have been affected by the highly-contagious illness, and the cases at Crisford's yard can be contained, it could yet be enough for the BHA to give the re-start a green light when they conduct their risk analysis.
A resumption could even happen while some stables, headed by McCain's Cheshire stable, remain in lockdown.
All horses in the Cleveland stable of trainer Rebecca Menzies, which had thrown up a 'suspicious' case, have now been cleared.
Sykes said yesterday: 'The data is encouraging and provides a further indication that the precautionary safety measures have helped to contain the spread of disease. However, the picture is still developing and it remains the case that we will make an evidence-based decision about the situation on Monday.
'The prioritisation exercise with regards to testing will help deliver a detailed picture of the spread of infection.' The BHA has received criticism from some trainers, who have accused them of over-reacting to the situation and pointed to the fact that Flu is endemic in the UK equine population.
But the BHA have hit back saying their actions have been driven by veterinary advice. They also pointed out that the Animal Health Trust had confirmed that a non-thoroughbred, unvaccinated horse had had to be humanely euthanized after having contracted the EI virus.
Sykes added: 'It remains paramount that, for the sake of our horse population, we do not take any unnecessary risks. This is not a common cold, it is a highly contagious and potentially serious disease.' ENDS