(Reuters) - The World Anti-Doping Agency (WADA) on Monday described allegations made in an Al-Jazeera report that Denver Broncos quarterback Peyton Manning took human growth hormone (HGH) as "very concerning" and has urged "increased collaboration" with sports leagues in the United States.
Though Manning has vehemently denied the allegations and the source of the Al-Jazeera report has since recanted the claims he was shown making in the film, WADA says that it expects a careful investigation by the relevant authorities.
The Dec. 27 investigative documentary 'The dark side: The secret world of sports doping,' linked well known players from the National Football League (NFL) and Major League Baseball (MLB) with performance enhancing drugs.