Son is one of four male weightlifters to have tested positive since standing on the podium in Tokyo, and the first whose case has been closed.

The other three, who are all provisionally suspended while proceedings are ongoing, are Anton Pliesnoi of Georgia, Zacarias Bonnat of Dominican Republic and the triple Olympic champion Lu Xiaojun of China.

The Kazakhstan Weightlifting Federation (WFRK) has stressed that Son will keep his bronze medal and the rewards that go with it, which include a $75,000 (£62,742/€71,057) cash payment and an apartment from the Government.

Moldir Abdualieva, spokeswoman for Kazakhstan’s Sports Ministry, said Son’s Olympic medal would not be withdrawn because the sample he provided in Tokyo was clean.

Son, 24, who competed in the 61 kilograms category, had been suspended before after testing positive for the banned steroid methandienone in 2015 when he forfeited a gold medal from the IWF Youth World Championships.

No substance was specified for his latest offence, which followed an out-of-competition test by Kazakhstan's national anti-doping agency last year.

Six weightlifters were caught last February and March as Kazakhstan, after years of doping violations that led to a slew of forfeited Olympic medals, adopted a "zero tolerance" policy to doping.

As well as Son, they included youth and junior world champions Rufina Chalkarova, 17, and Ablay Auyelkhanov, 19, plus a junior world silver medallist and two young athletes who had never competed internationally.

The WFRK said in a statement at the time, "Adhering to the policy of zero tolerance for doping, the WFRK intends to conduct an internal investigation into this incident."

The investigation appears to be ongoing, as no result has been announced.

The WFRK general secretary Aldiyar Nuralinov said yesterday, "This out-of-competition testing was taken after six months from those international competitions where the athletes took part, so there is no question of cancelling their results or returning medals.

"I would especially like to stress this with regard to Igor Son's Olympic medal."

Son, Chalkarova and Auyelkhanov won their medals six to 10 months before the out-of-competition samples were taken.

Son was his nation’s only male lifter in Tokyo, and like the lone female athlete Zulfiya Chinshanlo also won a bronze medal.

Because of Kazakhstan’s past doping record - its athletes forfeited six Olympic gold medals between 2008 and 2016 - it was one of several nations restricted to two quota places in Tokyo.

Chinshanlo was one of those who lost gold at London 2012, and the most high-profile "champion" was Ilya Ilyin, who was disqualified from Beijing 2008 and London 2012.

The International Testing Agency (ITA), which carries out all anti-doping procedures for the International Weightlifting Federation (IWF) has strengthened its relations with national anti-doping agencies, leading to more stringent local testing around the world.

While Son, who is banned until 2030, was caught and suspended at national level, the three other Tokyo medallists are all being dealt with by the ITA.

Pliesnoi’s case has dragged on for well over a year.

He tested positive at the 2021 IWF World Championships in Tashkent for ligandrol (SARMS LGD-4033), an androgen receptor modulator.

Bonnat returned a positive sample last November for a similar banned substance, the androgen receptor SARMS RAD140.

Lu was provisionally suspended in December after a sample taken out of competition on October 30 was positive for EPO, a substance that is popular in endurance sports such as cycling but which does not appear once on the list of sanctioned athletes on the IWF website, which covers doping violations since 2003.

Lu, who at 37 became the oldest Olympic weightlifting champion in Tokyo, had stated his intent to qualify for Paris 2024 but, regardless of what eventually happens with his case, he will be ineligible unless he is cleared to participate in a qualifying competition in May or June because he will be unable to make in the minimum number of appearances.