Four new sure tests for equine flu had been returned in vaccinated thoroughbreds at the Newmarket yard of flat coach Simon Crisford.
Racing is on elevate until at the least Wednesday while the British Horseracing Authority tests horses nationwide.
The suspension came after the invention on Thursday of six instances of equine flu at Donald McCain’s Cheshire staunch.
Crisford’s yard used to be named so “the Newmarket community is mindful” where the an infection has been found, the BHA acknowledged.
The yard is one of many 174 to be tested on story of runners from the staunch competed at the fixture at Newcastle on 5 February, which had been identified as a attainable misfortune fixture.
The entire affected horses are contained inner Crisford’s yard, the BHA acknowledged.
The BHA is decided to notify when racing can launch again on Monday evening.
The Animal Health Trust (AHT), which is conducting testing on behalf of the BHA, is working through “several hundreds of samples” bought from yards all over Britain.
Earlier on Sunday, the BHA reported that round 1,500 samples had been analysed without a sure test.
The authority furthermore confirmed that testing had been applied on the last 27 horses from the yard of Rebecca Menzies – where testing of three suspected instances came relief destructive on Saturday.
All horses within the yard contain tested destructive, but it completely will “live below close surveillance and extra testing will be applied”, the authority acknowledged.
Equine flu – now not in inequity to human flu – is endemic in Britain, where racehorses are vaccinated in opposition to it. The virus is typically now not regarded as life-threatening, but limits the aggressive ability of horses.
An unvaccinated non-thoroughbred horse used to be place down in Suffolk after rising considerations following a pandemic of equine influenza.
In a separate case, 10 unraced two-year-earlier thoroughbreds within the connected county had been found to contain shriveled the extremely contagious virus.
There had been outbreaks of equine influenza in 9 English counties since the launch of 2019.
One case involves a vaccinated non-thoroughbred horse in stables at a charge-paying college within the south west of England.
Cornelius Lysaght, BBC horse racing correspondent
Factual when folks had been thinking that the gentle at the end of the tunnel used to be getting brighter…
After two days of no sure test amongst a vogue of of swabs studied by scientists, the feeling used to be that the resumption of racing this week, per chance on Wednesday, used to be very principal on the cards.
Nonetheless this would appear to jeopardise that hope, for flat racing on the all-climate tracks anyway.
The Crisford operation at Newmarket is flat racing most productive, and there would possibly per chance be no obtrusive reference to the McCain string – undoubtedly the two stables contain had no runners at the connected venues of late.