The British Horseracing Authority has ended the lockdown of stables that had runners at Ayr last week, where Donald McCain-trained Raise A Spark ran before testing positive for equine flu.
While racing resumed on Wednesday with four meetings under strict bio-security controls, 22 trainers, many of them north of the border, remained unable to have runners.
But with frustration turning to anger among those trainers, the BHA now feel sufficiently reassured to act.
It avoids a potentially unfortunate situation at Kelso on Thursday.
Only two runners have been declared for the £25,000 Malcolm Jefferson Memorial Chase at Kelso but one of them, Captain Redbeard, could been forced out of the race with his trainer Stuart Coltherd among the trainers who had been barred because he had runners at Ayr.
That would reduced one of the feature races of the day to a walkover for Brian Ellison-trained Cheltenham Gold Cup outsider Definitly Red.
Coltherd-trained Leonasisland was one of five late withdrawals from Musselburgh yesterday where Irish-trained The Tartan Spartan was also barred from running after being transported from County Kilkenny.
The sport remains disrupted but the situation should ease over the coming days. There are only 28 runners at Leicester and 41 at Kelso. But nine of those at the Scottish track could have potentially been forced non-runners if the BHA had not made last night's announcement.
David Sykes, Director of Equine Health and Welfare for the BHA, said: 'The teams at the BHA and Animal Health Trust are working round the clock to analyse tests and clear horses to run.'
The mood in stables still in lockdown yesterday will not have been helped by the bizarre case of Grace Harris-trained Field Exhibition.
He won at Musselburgh yesterday but is not able to take up an entry at Market Rasen on Sunday because, by then, he falls foul of the BHA restriction that runners must have had an equine flu vaccination within the last six months.
The four horses from Simon Crisford's stable that had tested positive for equine flu have now returned negative results, the Newmarket trainer has revealed.