Reading's Sky Bet Championship match at home to Luton on Saturday has been postponed due to a Covid-19 outbreak, along with Millwall's game against Preston.
After QPR's visit to Swansea was also postponed, Reading said there had been a 'significant number' of positive PCR tests among both the first-team squad and under-23s.
A statement on the Reading website said: 'The club informed the EFL this morning that, following the return of a significant number of positive PCR tests within our first team and under-23 squads, we are unable to field a team capable of fulfilling the fixture on Saturday.