Reigning Olympic weightlifting champion Adrian Zielinski, from Poland, has been sent home from Rio after testing positive for nandrolone. The news follows positive tests for a Bulgarian runner and a Chinese swimmer.
Michal Rynkowski, the director of Poland's Commission Against Doping in Sport said on Friday that Zielinski, who won gold in the 85kg category in London in 2012, failed a doping test in Poland before the Games.
"I can clearly confirm that a urine sample taken from Adrian Zielinski gave a positive result for nandrolone. Its concentration was nearly twice the permissible norm," he said.
"Today we have received confirmation. The athlete faces a four-year suspension," he said.
Just two days before, on Wednesday, Zielinski, who had moved up to the 94kg category in Rio, said he'd never doped: "I deny taking anything. It's impossible," he said.
The news came just hours after Chinese swimmer Chen Xinyi and Bulgarian steeplechaser Silvia Danekova registered the first positive tests of this year's Games.
The 18-year-old female swimmer failed a doping test in Brazil on August 7, according to Chinese news agency Xinhua. Chen Xinyi finished fourth in the 100-metre butterfly on Sunday and was scheduled to compete in the 50-metre freestyle on Saturday.
Chen has asked for an examination of her B sample but "is provisionally suspended from competing at the Olympic Games Rio 2016", according to a statement from the Court of Arbitration.
The Bulgarian Olympic Committee also confirmed on Friday that both the A and B samples for Danekova were positive.
Danekova, 33, was tested on July 30 immediately upon her arrival in the Olympic Village and was found positive for the performance boosting eryrhropoiesis-stimulating agent (ESA), which stimulates red blood cell production. She has been suspended from Saturday's 3,000m steeplechase.
Late on Friday, a Brazilian cyclist who competed in the Rio Games has been provisionally suspended after failing an out-of-competition dope test in the lead up to the Games, the International Cycling Federation (UCI) said in a statement.