Middle-distance runner Regina Jacobs is the latest prominent athlete to test positive for THG, sources told The Washington Post for its Thursday editions.

On Wednesday, Dwain Chambers of Britain was named in a London newspaper as having tested positive for tetrahydrogestrinone, a designer steroid for which tests only recently were developed.

The Post reported last week that U.S. shot put champion Kevin Toth also tested positive for THG, which allegedly was distributed by Bay Area Laboratory Co-Operative (BALCO), a nutrition company with ties to star athletes who include San Francisco Giants slugger Barry Bonds.

Jacobs, 40, became the first woman to run 1,500 meters indoors in under four minutes (3:59.98) last winter. Two years ago, Jacobs became the third woman to win both the 800 and the 1,500 titles at the U.S. outdoor championships.

The Post reported that Jacobs did not respond to messages left by the newspaper for comment.