THE AFL admits the Essendon supplements saga might never have reached such a damaging scale if it had followed up earlier on a warning to Bombers coach James Hird.

Bombers assistant coach Mark Thompson, one of three officials penalised along with the club on Tuesday night, says the AFL could have reacted more strongly after becoming aware in mid-2011 that Hird had inquired about peptides.

Details of the charges against the Bombers released by the AFL last week included the allegation that Hird made an informal inquiry to an ASADA representative about whether other clubs were using peptides.

In response, at a meeting on August 5, 2011, Hird was warned by the AFL's integrity services manager that peptides were a serious risk to the League's integrity, in the same category as steroids and Human Growth Hormone.

Thompson confirmed on Tuesday night the warning was made, but that the club went ahead anyway with a supplements program including peptides.

But he suggested the AFL could have short-circuited the saga by following up on its warning.

AFL deputy chief executive Gillon McLachlan conceded on Wednesday that Thompson might be right.

"The fact that the club was warned I think is a credit to the AFL and the fact that we've got an integrity program that is trying to be ahead of the curve," McLachlan told SEN.

"The fact potentially though that we weren't out there regularly monitoring what was going on is potentially a failing of the AFL.

"There's responsibility all round here.

"I don't think that we can shirk it in every instance.

"I'm happy to take that on the chin in this instance.

"If we had gone out there every month and monitored it then maybe we wouldn't be in this situation."

Thompson said Hird's inquiry should have sounded the alarm for the AFL.

"All I'm saying is there was an awareness that something was happening," Thompson told the Nine Network's Footy Classified.

"We obviously went down a path, the alarm bells should have gone off in somebody's eyes.

"The AFL knew about this problem and what I would really like is that if they did know about the problem come and talk to the club, come and look inside our club, ask the questions and it might have been prevented."