An ashen looking Essendon coach and Bombers playing legend James Hird told a hastily called media conference at league headquarters that he was "shocked" with the stunning revelations.
He called for an inquiry resolution as soon as possible.
"Shock, is probably the best word," a clearly distressed Hird said.
"I'm shocked to be sitting here.
"We clearly don't want to be sitting here talking about this.
"We want to get this investigation started.
"We want to get it done and we want to come out with a clean bill of health and we want to move on with the footy season."
Hird confessed that he knew of substances his players were using through fitness and conditioning programs last season.
But he claimed that any substance use with Bombers players last season were approved by AFL medical lmitations and restrictions.
"The supplements that our players were given in my opinion and my knowledge, were all approved and within the rgeulation that we all play the game by," Hird said.
Essendon chairman David Evans announced the league's probe into use of substances that he revealed his club officials had only become aware of in the past two days.
Evans declared that the Bombers would cooperate fully with the investigation that will be as far reaching as inquiries from Australia's Sports Anti-Doping Authoritiy.
The probe will be handled by AFL chief investigator Brett Clothier and his team.
"Individuals is just not something I am prepared to talk about today," Evans said.
"There is an investigation going to start. We're focused on cooperating with the AFL and Brett Clothier and we're focused on working with ASADA.
"There's some things that I have learned in the last 48 hours and there's some things that I'm going to learn in the next 48 hours.
"It's a mission where we aim to get to the bottom of what's been going on and I feel confident that the action that we've chosen today is good governance."
Essendon sacked its sports science guru Stephen Dank late last year amid concerns about his conduct with players and a horid season with an alarming injury toll.
Just some key Bombers to miss bick chunks of an horrendous 2012 season included star forward Stewart Crameri, versatile big man Paddy Ryder, explosive on-baller David Zaharakis and big utility Michael Hurley all with soft tissue leg problems.
Dank was the major casualty from Essendon's disastrous season and savage review of football and sports science operations at the end of the season.
Dank is believed to have infuriated Bombers powerbrokers over his performance and the club's alarming injury crisis that ruined their 2012 finals chances.
Essendon crashed from a threatening fourth on the ladder after Round 14 to lose eight of their last nine matches and finished a dismal 11th.