Everton have requested full disclosure of all the information submitted by Manchester City to the Premier League after Monday's match was postponed.
The Premier League confirmed four hours ahead of the scheduled kick-off at Goodison Park that the game would not go ahead due to a coronavirus outbreak in City's camp.
Gabriel Jesus, Kyle Walker and another two members of staff had previously tested positive for COVID-19, but City's Boxing Day clash with Newcastle United still went ahead.
However, City lodged a request to rearrange the match with Everton 48 hours later following an increase in positive COVID-19 test results received earlier on Monday.
The Premier League Board agreed to reschedule the game as a precaution, saying the health of players and staff takes priority.
But Everton, one of only two clubs along with Merseyside rivals Liverpool able to welcome fans to their ground, are seeking further explanation as to why the game was called off.
A club statement read: "Everton Football Club regret the postponement of tonight's match against Manchester City - not only for the 2,000 fans who would have been attending, but for supporters on Merseyside and across the world.
"Our players were prepared for the game, as were both the team staff and everyone at Goodison. Matchday is the most important date in our calendar. And this was a big one.
"Whilst Everton will always have public safety uppermost, we will be requesting full disclosure of all the information that Manchester City provided to the Premier League so the club can be clear on why this decision was taken."
Monday's match is the second Premier League fixture to be postponed due to a coronavirus outbreak, with Newcastle United's game against Aston Villa this month also delayed.