The news coincides with Ukraine's Olga Abramova waiving the right to her B-sample being analysed after testing positive for banned substance only added to the banned list at the start of 2016. 

The decision leaves her facing the prospect of a four-year ban.

The second unnamed athlete tested positive for a substance included under the "hormones and metabolic modulators" category in the World Anti-Doping Code during an event in the IBU Cup, the tier below the World Cup. 

"In order to protect the affected athlete's personal right to confidentiality and the integrity of the results management process, the IBU will at this stage not release the name or nationality of the athlete," the IBU said in a statement. 

The IBU, meanwhile, has confirmed that Abramova tested positive for the metabolism booster meldonium while competing at the World Cup event in Ruhpolding in Germany on January 10. 

That was only nine days after the substance was officially added to the World Anti-Doping Agency's banned list.

Abramova had finished 25th in the women's 10 kilometres pursuit and 26th in the 12.5km mass start event. 

"The report from the laboratory in Cologne of the urine sample showed the presence of Meldonium," the IBU said in a statement.

"This substance was added to the WADA prohibited list in January, 2016.

"Meldonium belongs to group S4: Hormone and Metabolic Modulators.

"As the substance detected is prohibited under the applicable Prohibited List, the IBU will now initiate the disciplinary procedure, and the case will be assigned to the IBU Anti-Doping Hearing Panel for adjudication.

"With regard to formal procedure and according to the IBU Anti-Doping Rules, Art. 7.1.5, the A sample result is thus officially accepted by the athlete.

"The IBU Anti-Doping Hearing Panel will schedule a hearing of Ms. Abramova, which will be held in the near future."

Abramova told Ukrainian newspaper Segodnya she had taken meldonium, also known as mildronate, for a heart problem.

She claimed it was prescribed by her doctor but she stopped using it three weeks before it was banned.

It stayed in her system, however, she claimed. 

The 27-year-old was born in Ulyanovsk Oblast and originally competed for Russia.

She switched allegiance to Ukraine in 2012, however, believing it would be easier to make their team. 

Abramova's best performances were as members of Ukraine's relay team, which finished third in World Cup races last season in Antholz and Hochfilzen last December.