A Polish weightlifter who won gold at the 2012 Olympics is blaming a tainted supplement for the failed drug test that got him kicked out of the Rio games.

Adrian Zielinski, champion in the 85-kilogram class four years ago, had been due to compete in the 94kg division in Rio on Saturday but is instead back in Poland after testing positive for the banned steroid nandrolone.

The 27-year-old says he has "no idea" how nandrolone entered his body and says "something had to be polluted" among the nutrition supplements he takes, suggesting the Polish Weightlifting Federation could have given him poor-quality items.

Zielinski's younger brother Tomasz, the European weightlifting champion at 94kg, had already been sent home from Rio after testing positive for a nandrolone byproduct.