In a statement on her Twitter feed then, Yastremska said she was “astonished and under shock.”
“I firmly state that I have never used any performance enhancing drugs or any prohibited substances,” she said.
She said she passed a drug test at her most recent tournament, in Austria on Nov. 9.
Yastremska has won three WTA singles titles. She reached a career-high ranking of No. 21 a year ago. Her best showing at a Grand Slam tournament was reaching the fourth round at Wimbledon in her main-draw debut there in 2019.
“You can be assured that I am resolutely determined to do everything to clear my name,” Yastremska said.
The 2021 tennis season started this month, including a WTA tournament in Abu Dhabi, United Arab Emirates. The year’s first major championship, the Australian Open, begins Feb. 8 in Melbourne.
Yastremska had traveled to Melbourne aboard one of the Tennis Australia charter flights and was in quarantine pending the result of the ITF hearing.