Women's marathon world record-holder Ruth Chepngetich was provisionally suspended for a positive doping test on Thursday.

Track and field's Athletics Integrity Unit said Chepngetich tested positive for a banned diuretic and masking agent in March and "opted for a voluntary provisional suspension while the AIU's investigation was ongoing."

The Kenyan runner set the world record by almost two minutes at the Chicago Marathon last October in 2 hours, 9 minutes, 56 seconds. It was her third win in Chicago.

The moment Chepngetich set the record in Chicago is forever etched in the minds of runners and sports enthusiasts alike.

"A lot of us were there of course on that day, saw the race, saw the impact and how exciting it is to have a world record on the Chicago course," said Tim Bradley, executive director of the Chicago Area Runners Association.

The nonprofit Chicago Area Runners Association has more 10,000 members and is the third largest running club in the nation. Bradley says word of Chepngetich being provisionally suspended for a positive doping test is troubling news.

"Obviously, learning this news puts a lot of things into question, you know," Bradley said.

Chepngetich also won the marathon at the 2019 world championships in Qatar, where the women's race started at midnight to avoid extreme daytime heat.

The AIU gave no timetable for a disciplinary case for the 30-year-old runner.

Chepngetich was interviewed in person in Kenya in April and "complied with requests regarding our investigation," AIU official Brett Clothier said in a statement.

The substance Chepngetich tested positive for, hydrochlorothiazide or HCTZ, can be used to disguise the use of performance-enhancing drugs.

HCTZ is one of the most commonly prescribed diuretics in the United States. It is often used to treat conditions like high blood pressure and kidney disease.

"In the case of a runner or an athlete, hydrochlorothiazide might be used in a few different ways. One. It reduces your body weight — it's a diuretic — and so for a runner, maybe that makes them a little bit faster," said Dr. Melinda Ring, director of Northwestern Medicine's Osher Center for Integrative Health. "It also dilutes the urine because it's a diuretic, and then it can make it harder to detect banned substances because the dilution of the urine."

Ring said there have been cases where an athlete's supplements or medications were contaminated with HCTZ, but this did not seem to apply in Chepngetich's case.

"The level of concentration that was found in the urine sample of this particular athlete was extremely high," Ring said.

Chicago Marathon organizers released a statement on the provisional suspension, saying they are aware of the announcement and writing in part, "We will await the completion of the process by the AIU and any appeal by Chepngetich before providing further comment."

Full statement from Bank of America Chicago Marathon

The Bank of America Chicago Marathon is aware of the announcement by the Athletics Integrity Unit (AIU) regarding Ruth Chepngetich. We will await the completion of the process by the AIU and any appeal by Chepngetich before providing further comment.  

The Bank of America Chicago Marathon has and continues to be an advocate for strict anti-doping measures including drug testing procedures and protocols both in and out of competition. As a World Athletics Platinum Label event, every professional athlete who competes in the Chicago Marathon's professional athlete field is subject to the rules, regulations and anti-doping processes set forth by World Athletics, the World Anti-Doping Agency and the United States Anti-Doping Agency.