A decision on whether racing can resume next Wednesday will be made by the BHA on Monday.
While the McCain-trained runners who tested positive were not on track this week, the trainer had runners at Ayr and Ludlow on Wednesday and Wolverhampton on Monday. Trainers who had runners at those meetings have been asked to provide swabs of all horses in their yards for analysis.
BHA chief regulatory officer Brant Dunshea addressed the situation yesterday morning and said: "We've taken the decision to cancel racing in Britain until Tuesday inclusive in order to enable us to make a full assessment on Monday of whether we can return to racing on Wednesday.
"We haven't yet received the results from the samples that have been collected from the affected yard or any of the samples we've collected today from the potentially exposed horses from yesterday's fixtures.
"We know we're not going to be in a position, given the incubation period of the disease, to make a decision about returning to racing until first thing next week at the very earliest. We felt clarity for the industry was the most important thing at this challenging time."
Responding to the news, Newbury's chief executive Julian Thick said: "We're clearly disappointed, it's a major race meeting for us, but horse welfare comes first. We're as disappointed for the industry as we are for ourselves."
Asked whether the meeting could potentially be salvaged and re-staged, Thick added: "I think it's too early to say at this time. That's something we will be talking about with our sponsors, with some of the key trainers and with the BHA over the coming days.
"We're just letting all the customers who bought tickets, hospitality boxes and restaurant places know the bad news then we'll get round to thinking about the future after that."
Looking further ahead, the loss of meetings could have an impact on running plans for yards looking to ready horses for the Cheltenham Festival, which is due to begin on Tuesday, March 12.
In 2001 the meeting was cancelled due to the foot and mouth crisis, but with over a month until this year's meeting there is hope a similar situation can be avoided.
A statement by Cheltenham read: "We are in contact with the British Horseracing Authority on this matter, who are handling it on behalf of British racing and providing regular updates. The festival isn't for five weeks and we hope that the BHA's early actions will resolve this matter quickly."
Thurles staged the only meeting in Ireland as scheduled on Thursday, and runners from Britain will not be permitted to race in Ireland until further notice.
