Manchester City have confirmed defender Eric Garcia and a member of staff have tested positive for coronavirus.
The club made the announcement less than four hours before Sunday's scheduled Premier League match with Chelsea at Stamford Bridge.
"Both personnel will now observe a period of self-isolation in accordance with Premier League and UK Government protocol on quarantine," City said in a statement.
"Everyone at the club wishes our colleagues a speedy recovery ahead of their return to work, training and competition."
Manager Pep Guardiola confirmed on Friday that there had been three further positive tests for COVID-19 within his squad after an outbreak earlier in the week.
City's league game at Everton on Monday was called off and the Etihad Campus training centre closed after Gabriel Jesus, Kyle Walker and two further members of staff had returned positive tests.
Everton requested "full disclosure" of the information City provided to the Premier League, with the match being postponed four hours before it was due to start.
City resumed training on Wednesday, calming fears the game with Chelsea could also be rescheduled.
Earlier on Sunday, City said they were investigating after defender Benjamin Mendy was reported to have held a New Year's Eve party that included guests from outside his household, in breach of COVID-19 protocols.