The 24-year-old has tested positive for the banned substance letrozole, according to the Norwegian Dagbladet, citing a press release from the Italian anti-doping agency.
Letrozole is on the World Anti-Doping Agency's (WADA) list of prohibited substances and has previously been used by female athletes to lose weight.
Letrozole is also used to treat early-stage breast cancer, according to AFP.
Passler's best World Cup result this season is an 11th-place finish.
The biathlon competitions in the Olympics begin on Sunday with the mixed relay.
What do you think?