Two Australian Rules football clubs and a number of rugby league teams are being probed for the use of banned performance-enhancing drugs, officials said on Sunday.
Federal justice minister Jason Clare, criticised for releasing a damning report into doping in Australian sports last week that lacked details, confirmed that a number of clubs in the competing football codes were under suspicion.
Clare said authorities had passed on the names of the clubs to both of the sport's governing bodies.
"We've given the names of the clubs to both the NRL (National Rugby League) and the AFL (Australian Football League)," he told state broadcaster ABC.
"And the NRL and the AFL have asked for permission to tell the clubs that are affected by the investigation."
"The (Australian) Crime Commission agrees and we're taking action to allow both the NRL and the AFL to tell the clubs that are involved in this investigation," he added, referring to Australia's top criminal intelligence unit.
"And then it will be up to the clubs to put their hand up and say 'yes, we are one of the clubs that are affected by this investigation'."
One of the AFL clubs, the Melbourne-based Essendon Bombers revealed last week it was under investigation over the use of supplements given to players by team staff, and a senior AFL official said on Sunday that a second team was under suspicion.
"The AFL is aware of potential multiple breaches at (Essendon)," AFL deputy chief executive Gillon McLachlan told reporters.
"The AFL is aware of one case involving the possibility of WADA (World Ant-Doping Agency) prohibited performance-enhancing drug use by one player at one club."
McLachlan declined to name the second club, but added that the cases at Essendon may have involved the players being doped "without their knowledge or consent".
The NRL confirmed that multiple clubs were under suspicion, but would not inform them for "24-48 hours" for legal reasons.
"Once this information is passed on the NRL will not, under the guidelines outlined by the ACC, be able to identify the clubs publicly," the NRL said in a statement.
"This will be a matter for the individual clubs to consider in consultation with ASADA (Australian Sports Anti-Doping Authority), the ACC and the NRL."
The revelations come days after the release of an explosive government report that found "widespread" doping in both professional and amateur athletes Down Under.
The report, the result of a year-long probe by Australia's top criminal intelligence unit, has rocked the sports-mad country, with its Thursday release described as the "blackest day" in its sporting history by a former national anti-doping chief.
The probe into Essendon has also caused shockwaves, with senior club officials admitting at a media conference last week to concerns about the legality of their supplements programme which was administered to multiple players.
The club's players have admitted to having injections at clinics away from their training base and said they were told to sign consent forms.
Local bookmakers have suspended betting on Essendon's season-opening match on March 22 amid speculation from local media that the club may struggle to field a team if multiple players were stood down or suspended for doping offences.
McLachlan said that the investigations would likely take "months rather than weeks".
"It's not going to be as quick as everyone would like," he said. "The reality is that the investigators, which is ultimately ASADA in partnership with the AFL, have to get the right answers and that will take as long as it takes."
McLachlan added that the AFL was also aware of other cases involving illicit drug use among players.