US National Football League (NFL) says it is has launched a comprehensive investigation into the findings of an Al Jazeera documentary on sports doping in professional sports. The Al Jazeera investigation, broadcast last month, included the claims of a pharmacist who previously interned at an anti-ageing clinic in Indiana.He told an undercover reporter that the clinic shipped human growth hormone to the wife of star NFL quarterback Peyton Manning. On Tuesday, the NFL released a statement to US media saying that its review of the claims are ongoing and comprehensive. The statement added that the league was working with Major League Baseball and the US Anti-Doping Agency.