Saturday's Scottish Premiership match between St Mirren and Hamilton Academical has been postponed after the hosts' latest positive Covid-19 tests.
St Mirren had informed the SPFL they could not fulfil the fixture as they have only 11 registered fit players available.
The game has been postponed pending investigation by the league body.
St Mirren already face an SPFL probe after last Saturday's game against Motherwell was also called off.
The news comes as the SPFL revealed it has opened disciplinary proceedings against Kilmarnock, claiming a breach of Covid-19 protocol, after their top-flight game against Motherwell on 3 October was postponed.
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The SPFL said St Mirren had informed them that "due to a number of positive tests for Covid-19 amongst their playing squad and coaching staff, and a number of other players who are isolating, they have only 11 registered fit players available".
St Mirren added in a statement that Public Health Scotland had placed the entire first-team and coaching staff into isolation.
"We appreciate this is a frustrating situation for all connected to the club and those involved at Hamilton Academical," chief executive Tony Fitzpatrick said.
"This continues to be a challenging time for the club, but the health and wellbeing of our players and staff remains our utmost concern."
European governing body Uefa's guidance - which has been adopted by the SPFL - says a fixture can go ahead as long as a team has 13 available players, including at least one goalkeeper.
After last weekend's game was postponed three hours before kick-off, with St Mirren saying they only had eight available players, the club had confirmed further positive coronavirus tests after routine screening this week.
St Mirren have had the most instances of positive tests in Scotland's top flight, with the first relating to an outbreak in July with seven coaching staff, only for it to later emerge six positives were false.
In September, the Paisley club then had to sign Zdenek Zlamal on an emergency loan after all three of their goalkeepers were ruled out of a game against Hibernian.
Their next match is scheduled to be against Dundee United on Friday, 6 November.
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