Only one of the seven St Mirren staff members who tested positive for Covid-19 actually has the illness.
The Paisley side said on Thursday that the individuals - none of whom are players - had been identified after tests analysed by a private lab.
However, after further NHS screening, it has emerged that six staff members returned 'false positives'.
The other is in "strict isolation" and has not been in contact with any player or other staff member since Saturday.
"The club will continue to support and look after this staff member to ensure a full recovery," added chief executive Tony Fitzpatrick, who confirmed Saturday's friendly with St Johnstone remains cancelled.
Fitzpatrick said St Mirren had "complied robustly" with testing protocols "to the letter" and are "undertaking an urgent review of the private testing arrangement".
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As a consequence of the results, Scottish Premiership clubs have had to reintroduce twice-weekly testing for the first time since 8 July.
The news comes after the Scottish FA wrote to Rangers, Motherwell and Hibernian to ask them to explain delays in receiving test results.
The Ibrox side have also been asked whether they breached protocols by fielding players who had not received up-to-date results against Dundee United on Wednesday.
The rules state players cannot take part in matches unless a negative test has been returned, with another Rangers friendly later that day against Motherwell delayed for two hours while both sides waited for results.
Hibs' friendly with Ross County was cancelled at short notice on Saturday for the same reason.
The governing body had already reminded clubs of the importance of adhering to the protocol, with the Premiership season scheduled to start on 1 August.
At this stage, there remains no suggestion that is in any doubt.
St Mirren, who are due to begin their competitive campaign at home to Livingston in little over a week, last played Hamilton Academical in a friendly on Saturday.
All Hamilton players and staff were tested two days after that, with no positive tests returned.
The club also confirmed that the area of FOYS Stadium used by St Mirren was segregated, then cleaned and disinfected afterwards.
Scottish football's coronavirus joint response group (JRG) informed the Scottish government of the tests before demanding clubs "revert to twice-weekly testing protocols until further notice".
However, SPFL chief executive Neil Doncaster said: "There can be no complacency, but we are heartened by the rigorous way that clubs, players and officials have responded to Covid-19 since March.
"With such regular testing being carried out by SPFL clubs, it is inevitable that several players or coaching staff will have tested positive. This has happened, as it has also happened in leagues around the world.
"What is vital is that clubs manage those very few confirmed positive tests such that the virus does not spread. So far, the rigorous work that our clubs have carried out has ensured that this is the case."