Five Jamaican athletes, including Asafa Powell, have tested positive for banned performance-enhancing drugs, according to the country's anti-doping authority.
Herb Elliott, chairman of the Jamaican Anti-Doping Commission (JADCO), confirmed the body had received "reports of adverse analytical findings from 'A' samples."
He said: "The process of the result management has commenced in accordance with the JADCO anti-doping rules.
"We cannot disclose any further information until the athletes have responded to notification of the 'A' sample."