All 44 athletes on the Jamaican team, including sprint superstar Usain Bolt, were tested Monday at their Moscow training camp for the athletics World Championships.
Team officials confirmed that agents from the World Anti-doping Agency (WADA) arrived at the camp in Moscow, where all of the athletes had blood taken in the sweeping operation.
It wasn't clear if an entire national team had ever before been asked to undergo testing on the eve of a major competition. (Also read: Mo Farah challenges Bolt to race for charity)
The Jamaican track and field program has been under increased scrutiny over the last two months after former World 100m record holder Asafa Powell and his training partner Sherone Simpson were among five athletes who tested positive at the Jamaican championships in Kingston in June.
Powell and Simpson returned positive tests for a stimulant oxilofrine, results that came just weeks after two-time Olympic women's 200m champion Veronica Campbell Brown also returned a positive test at a meeting in May.