(CBS) – A two-time Chicago marathon winner has tested positive for banned substances.

Rita Jeptoo called herself the “Queen of Chicago” after winning her second straight Chicago title in October.

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The Kenya native tested positive in her home country for a banned “endurance-boosting” drug in September. A second sample from the same test came back positive today.

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Carey Pinkowski, executive race director for the Chicago Marathon, says it’s unclear how this will affect Jeptoo’s standing here.

“We are disappointed by this news,” he said in a prepared statement. “We must respect the process and will await the International Association of Athletics Federation’s formal proceedings and final ruling before addressing the athlete’s standing.”

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If Jeptoo is stripped of her Chicago title and prize money, she would become the fourth Chicago Marathon women’s winner to lose the title for doping in six years.