Leyton Orient's League Two match at Walsall on Saturday has been suspended as O's players and staff isolate after a Covid-19 outbreak at the club.
BBC Sport has learned that Orient, whose Carabao Cup tie against Tottenham on Tuesday was also called off earlier this week, returned 17 positive tests.
Orient advised the English Football League that they felt "unable to safely fulfil" Saturday's fixture.
The EFL said it would investigate the circumstances of the postponement.
No date for the rearranged fixture has been set as staff and players self-isolate in accordance with both the league and government guidance.
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