(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.

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.

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.”

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.