(Reuters) - Aston Villa's FA Cup third round-match against Liverpool on Friday is in doubt after Villa reported new COVID-19 cases in their first-team squad.
Villa closed their training ground and cancelled Thursday's practice session, as a number of players and staff went into isolation.
"A second round of testing was carried out immediately and produced more positive results today," Villa said in a statement.
The FA said later on Thursday that a final call on the game would be taken on Friday after the results of additional tests were known.
"The FA and Aston Villa are working closely together to try to ensure that the club's FA Cup third round tie with Liverpool can go ahead as planned at Villa Park tomorrow evening," the FA said.
Earlier, the FA said Southampton's FA Cup third-round match at home to Shrewsbury Town will not take place as scheduled on Saturday after the third-tier team reported several COVID-19 cases in their squad.
Shrewsbury told the FA that due to the "significant number" of cases, they did not have enough fit players who were not in self-isolation to fulfil the fixture against the high-flying Premier League side.
"Shrewsbury Town provided the FA with details of the medical advice it had received and its communications with local Public Health England and liaised with the FA's COVID Medical Officer for the FA Cup," the FA said.
"The FA also requested and considered further information regarding Shrewsbury Town's ability to fulfil the fixture."
The FA said there will be a meeting of its Professional Game Board next week to decide on the fate of the fixture.
Championship (second-tier) side Middlesbrough also said preparations for their third-round match at Brentford had been affected after a number of their first-team players and staff tested positive.
Derby County said on Wednesday that their first-team squad and interim manager Wayne Rooney would play no part in Saturday's FA Cup match at sixth-tier Chorley as they were self-isolating after an outbreak of the virus at the club.
But the game is due to go ahead with Derby set to pick a team predominantly made up from the club's Under-23 and Under-18 squads with youth coaches taking charge.
COVID-19 outbreaks have led to four Premier League matches being postponed and more than 50 games in the lower divisions of the Football League (EFL) being called off this season.
(Reporting by Rohith Nair and Hardik Vyas in Bengaluru; Editing by Ken Ferris and Ed Osmond)