Peterborough have confirmed that the club's next three Sky Bet League One fixtures have been postponed following a positive Covid-19 test within the squad.
As well as the unnamed player testing positive, three others are displaying symptoms.
Posh, who are third in the table, were set to host Ipswich on Saturday, but that match will now be rearranged, with the trip to Gillingham on Boxing Day and the visit of Charlton on December 29 also being postponed.
A club statement read: "Peterborough United can confirm that our scheduled Sky Bet League One fixtures with Ipswich Town, Gillingham and Charlton Athletic have been postponed.
"The club can confirm that an unnamed player has tested positive for Covid-19 and three others are displaying symptoms. The safety and health of our players is paramount. The club have notified the EFL of the postponements.
"The next scheduled league fixture is on 2nd January 2021 against Doncaster Rovers at the Weston Homes Stadium. The club will be making no further comment."
On Thursday, the Government announced Peterborough was to move into Tier 3 restrictions, meaning games at London Road would revert to being played behind closed doors.
As with all fixtures which are postponed because of positive coronavirus cases, the EFL will open an investigation.
A statement from the governing body read: "Peterborough United's next three Sky Bet League One fixtures against Ipswich Town (Saturday 19 December), Gillingham (Saturday 26 December) and Charlton Athletic (Tuesday 29 December) have been suspended.
"The club informed the EFL that they would be unable to fulfil the fixtures following a recent positive COVID-19 test and the requirement for players and staff to self-isolate for 10 days as per EFL and Government guidance in order to mitigate against the risk of further infection.
"The circumstances surrounding the postponements will now be the subject of an investigation in accordance with EFL Regulations.
"Revised dates for the rearranged fixtures will be confirmed in due course."