ADELAIDE chief executive Andrew Fagan says the Crows made an "honest mistake" when they breached social distancing rules while training in quarantine in the Barossa Valley.

Sixteen Crows players and assistant coach Ben Hart are completing a mandatory 14-day period in isolation after returning to South Australia from interstate as football prepares to resume after its COVID-19 shutdown.

However the Crows on Thursday broke rules and trained in groups of eight instead of the mandatory two under AFL rules.

Fagan, who apologised to AFL boss Gillon McLachlan on Thursday, explained the breach on Friday and said it wasn't a deliberate move.

"We had 16 players return from interstate, we had approval from SA police to train down at that facility, which is a 20-acre facility, so it's got some ability for the players to not just be in their rooms but to move around and do some running and training," he told SEN.

"But the expectation that was clearly articulated was to be in pairs and was to maintain social distancing. This was their first session there and it appears as though the communication about how the first session was to be conducted wasn't anywhere near as clear as it needed to be.

"I saw a copy of it last night – it refers to social distancing, it refers to training in pairs, and they did that for a number of elements of the session. But for others they came together beyond their pairs, I think as a group of eight and they breached some of those social distancing rules.

"That's what's occurred. I think it's an honest mistake but it's a serious one. We understand where the industry's at in these discussions and everyone's pretty frustrated."

The AFL is investigating the incident and a penalty is expected in coming days, although Fagan could not be drawn on whether players involved could be suspended.

The breach couldn't come at a worse time, with the League currently in negotiations and discussions with state governments throughout the country on its hopes to restart the competition next month.

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Fagan said he hoped the Crows' slip wouldn't put any plans at jeopardy as it "wasn't intentional".

"This is our error. There's no walking away from it. We made a mistake and we accept that. It's been hammered home to us as an industry with our club and the other clubs about the adherence to the AFL protocols and the broader community protocols," he said.

"We know this is a community issue and we're all expected to play our role in flattening the curve and we're not shying away from that."