Uzbekistan's Nodirbek Shavkatov on Sunday became the first medallist at the Asian Games in Japan to test positive for doping, testers said.
Shavkatov, who won bronze in mixed martial arts in Aichi-Nagoya, is the third athlete at the Games to fail a drugs test.
Shavkatov has been provisionally suspended after testing positive for the banned substance meldonium, the International Testing Agency said.
It came a day after Dayanch Keletliyev of Turkmenistan, who competed in karate, also returned a positive test for meldonium.
The drug is a prescription heart medication that can improve endurance and accelerate muscle recovery.
Shavkatov has the right to challenge the provisional suspension and request analysis of the B-sample.