Officials from most sports say they have no knowledge of their athletes testing positive to the banned stimulant that showed up in tests on nine Australian athletes.

The Australian Sports Anti-Doping Authority (ASADA) on Saturday confirmed the positive results for methylhexaneamine, or DMAA - a substance commonly found in body building and dietary supplements - with all nine athletes now facing possible two-year bans.

The AFL, Athletics Australia and a host of other sports claimed either their athletes weren't involved or that they had no knowledge of positive tests in their respective sports.

But the National Rugby League released a statement admitting four players from lower level competitions were under investigation over the use of the banned substance.

It is not known if those four players - one from the national under 20s competition and another three from NSWRL-run competitions - are among the nine positive tests announced by ASADA.