Racing has been suspended at a track in the United States after 15 jockeys tested positive for coronavirus.
Meetings scheduled for Friday, Saturday and Sunday at Del Mar will not be held.
All jockeys set to ride at the track in California were checked after leading riders Flavien Prat and Victor Espinoza tested positive.
Officials say the affected jockeys were asymptomatic, are isolating at home and they hope to resume action at the course on 24 July.
“Assuming these individuals continue to show no symptoms, they will be isolated for a total of 10 days and should be able to resume their usual activities, including riding after that time,” said Dr Eric McDonald, medical director of San Diego epidemiology and immunisation department.
The season at Del Mar began on 10 July without spectators because of the coronavirus pandemic.
Safety measures for those taking part included temperature checks, face covering and social distancing requirements, additional hand washing and sanitiser stations, and regular disinfecting of all common areas.
Del Mar chief executive Joe Harper said: “Cancelling this weekend’s races will give us additional time to monitor the situation and give the individuals who tested positive additional time to recover.”
Espinoza rode American Pharoah in 2015 to become the first US Triple Crown winner for 37 years.
Umberto Rispoli, another jockey to test positive, said: “I’m feeling more than well, quarantined, and looking forward to coming back stronger then before.”
All but one of the jockeys rode at the recent meeting at Los Alamitos in California.