The wave of meldonium positive drug tests has hit the UFC.

Daniel Omielanczuk, a heavyweight competitor, tested positive for the prohibited substance in a recent out-of-competition test and has been notified of a potential anti-doping policy violation by USADA, the UFC announced Friday.

Omielanczuk, though, will not be provisionally suspended due to continual questions about the drug. The Polish fighter will still face Alexey Oleinik at UFC Fight Night: Lineker vs. McDonald on July 13 in Sioux Falls.

Meldonium, which has been prevalent in test samples taken from Eastern European athletes, was placed on the World Anti-Doping Agency (WADA) banned list on Jan. 1, 2016. It remains unclear how long the substance stays in a person's system, so it's possible Omielanczuk took it before it was banned. There are also questions about whether or not meldonium is a performance enhancer.

Tennis superstar Maria Sharapova tested positive for meldonium earlier this year and was suspended for two years by the International Tennis Federation.

WADA announced in April that more studies needed to be done on meldonium with regards to how long it remains in the blood stream. Any samples taken before March 1 or containing less than one microgram of meldonium may be permissible, the agency said.

Omielanczuk (18-5-1, 1 NC) has won two in a row in the UFC and is coming off a majority decision over Jarjis Danho in February.