American tennis player Varvara Lepchenko has been handed a four-year ban for doping after being provisionally suspended in August 2021.
Lepchenko tested positive for a banned stimulant during the Hungarian Grand Prix in July.
She told an independent tribunal she did not intentionally ingest the drug and could have unknowingly taken it.
"[We found] the evidence provided by the player to be vague to the point of non-existent," the tribunal said.
They added: "[This is] in respect of what, when and in what doses the supplements were taken, especially in the period immediately prior to the positive test.
"There is in fact no evidence whatsoever that the supplements referred to by the player were the source of the prohibited substance detected."
The ban has been backdated to August.
It is a second doping offence for the Uzbek-born player, who switched allegiance to the United States in 2007, but it is being treated as her first violation for the purpose of punishment as she was deemed not to have been at fault in the previous case.
In 2016, Lepchenko was among a number of athletes from various sports who tested positive for Meldonium, which saw her fellow tennis player Maria Sharapova banned, but was deemed to "bear no fault or negligence" by the International Tennis Federation.