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

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

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.”