McKenna, who returned from his native Ireland last month, had been due to feature in the round three game at the MCG but tested positive for COVID-19 on Saturday.

"Conor McKenna returned a low-grade irregularity yesterday after being tested as part of our COVID-19 protocols," AFL chief executive Gillon McLachlan said, when announcing the match was postponed.

"He was tested again today and we were informed this afternoon that the test came back (positive).

"The health department has been notified and we will be working with (them) to identify close contacts and isolate them.

"At the moment all players and football department staff have been told to isolate until that work is done."

It remains unclear if the game will be rescheduled or whether Essendon will be allowed to play their round four clash against Carlton at the MCG.

The Bombers are awaiting further advice from the Department of Health and Human Services in the next 24-48 hours as to how long their players and staff will have to self-isolate and when they could return to training and playing.

"We do (plan to play Carlton) until we take advice that tells us something else," Essendon chief executive Xavier Campbell told reporters.

"Clearly I wish this situation hadn't come about and I feel for Conor and the group because it has.

"But given the flexibility the league's put in place, I feel like we will be well placed to work through that."

Campbell said Essendon's football department had followed protocols "completely" on Saturday and the club would be closed for at least the next 48 hours for thorough cleaning.

He emphasised the Bombers would look to support McKenna, his teammates and club staff.

McLachlan revealed McKenna had been tested five times while in hotel quarantine on his return from Ireland and had returned negative results each time.

McKenna was kept away from a training session on Saturday morning after returning the irregularity on Friday, following Essendon's main full-contact session.

"He was tested on Wednesday and was negative and there was such a low level in his test on Friday that it came up as an irregularity," McLachlan said.

"And then it was a positive test (on Saturday) morning.

"So based on those facts, he's picked it up this week here in Australia. But again, I will defer to the health department.

"They are the facts as we know them."

"I don't have an answer (yet) but what I do know is we have time and flexibility," McLachlan replied, when asked about rescheduling the Melbourne match.

"Whether we compress the season or whether there ends up being a bye ... it's why we've got this rolling four-week fixture and shorter quarters, so we've got the flexibility to deal with this."

Starting times for Sunday's other matches, both at Metricon Stadium, were moved following the postponement.

Gold Coast and Adelaide's clash will move from 1:05pm (AEST) to 3:05pm, while Fremantle and Port Adelaide's match starts at 8.10pm, two hours later than originally scheduled.

Australian Associated Press