Call it "Black Sunday" for the sport of track and field.

Hours after news broke that American sprinter Tyson Gay tested positive for a banned substance, two marquee Jamaican athletes acknowledged that they, too, had failed drug tests.

Asafa Powell, who won a gold medal in the 400-meter relay at the 2008 Summer Games, and Sherone Simpson, a three-time Olympic medalist, expressed dismay at the results.

"I want to be clear in saying to my family, friends, and most of all my fans worldwide that I have never knowingly or willfully taken any supplements or substances that break any rules," Powell said in a statement sent to The Times. "I am not now — nor have I ever been — a cheat."

This was supposed to be an exciting time for track and field, just weeks before the world championships in Moscow.

Fans were particularly excited about seeing Gay, who owns the fastest 100-meter time in the world this season, race against Usain Bolt. The American announced he will withdraw from the championships.

A month ago, another Jamaican star, Veronica Campbell-Brown, tested positive for a banned diuretic.

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