Park, one of South Korea's most decorated athletes, received chiropractic treatment at a local hospital prior to last year's Asian Games, when he was given an injection that contained a banned substance, news agency Yonhap reported his management agency as saying.

"At the time, the hospital offered to give Park an injection and he repeatedly asked if it contained any illegal substances," the management statement said.

"The doctor said there would be no problem. And yet it turned out the injection contained a banned substance.

"He hasn't even taken cold medicine so that he wouldn't fail doping tests. Park is more shocked by this result than anyone else."

The agency said they were planning to take legal action against the hospital.

Cornel Marculescu, executive director of world swimming body FINA, declined to comment to AFP, saying only that FINA's anti-doping commission would meet in late February.

Park won 400m freestyle gold and 200m freestyle silver at the Beijing 2008 Olympics, becoming South Korea's first Olympic swimming medallist.

He also won silver in both events at the 2012 London Olympics, along with 400m gold in the world championships in 2007 and 2011.

The 25-year-old swimmer had a disappointing time in the pool in front of an expectant home crowd at the 2014 Asian Games, managing only a silver and five bronzes.

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