LAUSANNE, SWITZERLAND -- Argentine swimmer Guillermo Bertola has been banned for four years and stripped of his 2019 Pan American Games silver medal in a doping case in which he said he received a transfusion of his mother's blood.

The governing body of swimming said Thursday the case against the 30-year-old open-water swimmer was based on irregular blood readings in his biological passport.

When Bertola was contacted for the investigation, he blamed altitude training and the "use of a snorkel and mask with hypoxic effect," FINA said.

He later acknowledged getting a blood transfusion in January 2018 while sick with gastrointestinal problems.

Bertola's mother testified at a hearing conducted by video link, and the FINA judging panel noted a "troubling general lack of detail in the testimony."

Bertola has been banned until January 2024. He will lose all medals and prize money gained since January 2018, including his silver medal in the 10-kilometre race at the 2019 Pan Am Games in Lima, Peru.

He also took bronze at the 2011 Pan American Games and represented Argentina at four world championships.