Essendon's sports science team allegedly bypassed the club's AFL-accredited medical staff and used at least one external doctor to assist in a supplements program at the centre of an anti-doping inquiry.
Fairfax Media can also reveal the doping affair has spread, with an official involved with a Australian professional road cycling team linked to performance enhancing hormone peptides.
The Bombers' sports science team is understood to have engaged the services of at least one, and possibly two, external Melbourne doctors with limited sports medicine expertise to participate in the player's supplements regimen between late 2011 and mid-2012.
Medical sources aware of the arrangement have alleged that one of the external doctors involved may have written prescriptions for the players to be issued with supplements.
Essendon's long-standing and respected club doctor, Bruce Reid, is understood not to have been aware that the players supplements regime involved doctors from outside the club.
The external doctor involved has refused repeated requests to discuss his role in the supplements program.
The Australian Sports Anti-Doping Authority is investigating Essendon's supplements program for the 2012 season. The club and its former sports science chief, Stephen Dank, have denied any performance enhancing drugs were used.
But the club and its players could face sanctions if it is established that the injections given to players breached the AFL's rules on intravenous infusions.
A spokesman for Essendon declined to comment on the alleged use of external doctors, citing the ongoing anti-doping probe.
It has previously been reported that two former Essendon players confirmed players were injected in the stomach by a club high-performance official and fed supplements intravenously at a nearby Botox clinic.
Australian Medical Association Victorian president Stephen Parnis said although he did not want to directly comment on the Essendon situation, it was an established principle that the use of dual doctors could result in "potential harm" to patients if either was not informed of what the other had prescribed.
"There's always the potential for adverse reactions to medications," Dr Parnis said.
He said doctors were ethically obliged to act in the best interest of individual patients and "should not be afraid to tell a patient, an employer or even a sporting club things they might not want to hear".
Greg Stanton, a lawyer for Dank, declined to answer questions about the alleged use of external doctors at Essendon last year, saying his client had nothing further to add to what he said on the ABC's 7.30 earlier this month.
Invoices obtained by Fairfax Media show that Dank, in his capacity as Essendon's sports science chief, operated an account with South Yarra compounding pharmacist Nima Alavi.
As a compounding pharmacist, Mr Alavi is licensed to import and sell peptides to patients with a prescription.
He has declined interview requests, but through his lawyer, Jack Bock, has strongly denied any wrongdoing.
Dank has denied providing any banned substances to players. He told 7.30 that Essendon's coaching and medical staff were fully aware of his supplement regime for the players.
He also alleged several Essendon coaching staff took substances that were did not comply with the ASADA and World Anti-Doping Authority's code.
Fairfax Media has confirmed that Mr Alavi was asked by a Melbourne doctor to provide a peptide hormone known as CJC 1295 to a man believed to an official of an Australian professional road cycling team.
Under ASADA's rules, team officials can be disciplined for possessing banned substances, such as CJC 1295 which acts as a growth releasing hormone.
The cycling official did not return calls. ASADA is understood to be assessing his situation.
Mr Alavi's lawyer, Mr Bock, last week stated in a letter that his client "wishes to stress that he supplies peptides to patients and, although under no legal obligation to require the same, only on prescription by a medical practitioner".
"My client only dispenses medication to individual patients and does not supply any clinics or sporting bodies with medication. My client does not supply any performance enhancing drugs [including peptides] to any AFL player or other professional sportsman," Mr Bock wrote.
Mr Alavi's pharmacy website was this month promoting a banned hormone peptide called GHRP-6 as "coming soon".