Turkey's Adem Kılıççı has been provisionally suspended by the International Boxing Association (AIBA) after becoming the latest athlete revealed as having tested positive following re-analysis of doping samples from the 2012 Olympics in London.
Kılıççı reached the quarter-finals in the under 75 kilogram category at London 2012, losing to eventual gold medallist Ryōta Murata of Japan.
He won a bronze medal at the 2007 World Championships in Chicago, as well as a European silver in Ankara in 2011.
The 30-year-old, who also competed at Beijing 2008, had already qualified to represent Turkey at Rio 2016.
He has now been suspended and will be unable to compete in the Brazilian city, an AIBA spokesperson told insidethegames here today.
It follows the International Olympic Committee (IOC) retesting samples from Beijing 2008 and London 2012, focusing on those hoping to compete at Rio 2016.
Thirty-two Beijing 2008 and 23 London 2012 positive results were registered, with the full list of names yet to be confirmed.
Kılıççı is the only boxer involved, AIBA claimed.
It comes after hammer throw gold medallist Tatyana Beloborodova was identified by public sports channel Match TV as one of eight Russians who also tested positive following re-analysis of London 2012 samples.
Shot put silver medal winner Yevgeniya Kolodko is the only other one to have been named so far.
Fourteen named Russians also failed in Beijing, including nine medallists who won a total of eight medals.
These included Yuliya Chermoshanskaya, a member of the gold medal winning 4x100 metres relay quartet, and bronze medal winning high jumper Anna Chicherova, a major icon who won gold four years later in London.
The only other athlete from outside Russia to be named as having failed is Spanish hurdler Josephine Onyia, who has been implicated in the fifth doping scandal of her career.
Turkey has a terrible doping record in recent years, with 31 athletes from the nation having been handed suspensions in 2013 alone.
"The Turkish Olympic Committee is extremely disappointed by the positive result following the retesting of Adem Kılıççı’s sample from the London 2012 Olympic Games," the body told insidethegames in a statement.
"The TOC has a zero tolerance policy on doping and any form of cheating in sport and our primary objective is to protect clean athletes.
"We will now follow the official procedure and will announce appropriate action in due course.
"In the meantime, we are redoubling our efforts to encourage more rigorous testing in parallel with greater education of all athletes and their entourages throughout Turkish sport.
"The TOC fully supports the IOC and WADA’s actions in their drive to clean up world sport and we are determined to play our part in this fight."
It is not clear if any other Turkish athletes are involved.
But Turkish newspaper Milliyet has suggested today that 1500 metres runner Gamze Bulut will be stripped of her London 2012 silver medal after she was reported as having failed a drugs test in March.
Bulut's compatriot Aslı Çakır Alptekin won the 1500m race at London 2012 but has since been given an eight-year ban and has been stripped of her gold medal.