* Athlete said positive test through contamination
* Lawson won silver in 2017 world championships (Updates with Lawson reaction)
BERLIN, Aug 31 (Reuters) - American long jumper and sprinter Jarrion Lawson blamed contaminated beef after the Athletics Integrity Unit (AIU) said on Friday that he had been provisionally suspended following a positive test for a banned substance.
Lawson, who won silver in the long jump at last year's world athletics championships, tested positive for epitrenbolone, the AIU said.
"AIU confirms a provisional suspension against USA sprinter and jumper Jarrion Lawson for the presence of epitrenbolone, a violation of Article 2.1 of the IAAF Anti-Doping Rules," it said on Twitter.
The 24-year-old athlete denied any wrongdoing saying the substance could have entered his body through the consumption of beef. He said a June 2 sample had tested positive for the substance and he was notified on Aug. 3.
"Having now researched Trenbolone, we have discovered that it is a USDA approved steroid, legally used in the United States in the production of beef," he said in a statement.
"Lab results have shown that there were extremely trace amounts of the metabolite in my sample. We are confident that we will prove that the metabolite entered my system through contamination."
"I am a 100 percent clean athlete and a big supporter of a clean sport. I am completely confident that a fair decision will be made in this case and I will be cleared of any wrongdoing."
Lawson had finished just outside the medals, in fourth place, at the 2016 Rio de Janeiro Olympics.
The AIU, in charge of drugs testing in athletics, was set up a year ago as part of the world athletics body IAAF’s efforts to separate itself from anti-doping testing and corruption and rebuild athlete and fan confidence in the sport. (Reporting by Karolos Grohmann Editing by Toby Davis)