Antonis Martasidis is one of the of two athletes to be sent home on Saturday (7 August), following the suspension of Irish boxer Michael O'Reilly on Thursday. Martasidis, a Cypriot weightlifter, and an unnamed Greek competitor bring the total number of new cases since the start of the competition to three.
Both the Greek and Martasidis were tested for banned substances in July. The Hellenic Olympics Committee confirmed the expulsion of a Greek athlete on Friday, although the individual cannot be named before their B sample is also tested, after the results of a test taken place on 5 July.
Greece's Olympic body announced in a statement on its website: "The Administrative Board of the Hellenic Olympic Team in Rio announces that a first sample of a member of the Olympic Team was found positive during a doping control taken place at the beginning of July in Athens.
"The HOC had requested the control of all Greek athletes who were going to participate in the Rio Olympic Games. The above-mentioned member of the Hellenic Olympic Team has left the Olympic Village."
Irish boxer O'Reilly became the first athlete at the competition to fail a drugs test, it was announced on Thursday. The 23-year-old 2015 European Games gold medalist faces a provisional suspension until an investigation is completed.
The event in Rio has been marred by doping after the World Anti-Doping Agency (Wada) exposed what it called a "state-sponsored" doping programme in the Russian team. The findings of the investigation led to the ban of 118 Russian athletes from this summer's Olympics, including tennis ace Maria Sharapova, who failed a drugs test during the Australian Open in January.
Once the Olympics are underway, athletes must adhere to the International Olympic Committee's (IOC) testing rules from the opening of the athlete's village to the closing ceremony, during which time athletes can be tested at any time, at random, when they are in or out of competition. Athletes must also provide details of their whereabouts, to ensure it's possible for out-of-competition testing to take place if they are selected.
However, Wada announced in June that it had suspended the accreditation of the Brazil's only doping laboratory.