Besiktas executive chairman Ahmet Nur Cebi is among a spate of positive coronavirus tests in Turkish football.
Shortly after revealing eight unspecified individuals related to the club had contracted Covid-19, Besiktas on Thursday confirmed Cebi had returned a positive result.
The team have reportedly stopped training, with the Super Lig set to return from its suspension during the pandemic on June 12.
A statement from Besiktas' health team consultant Tekin Kerem Ulku said: "The follow-up and treatment process of the people whose test results were positive has started immediately in line with the relevant procedures."
Fellow Super Lig side Kasimpasa then revealed two players at the club had tested positive and would be quarantined, although they did not reveal the identities of those infected.
On Wednesday, second-tier outfit BB Erzurumspor said their latest round of testing returned 11 positive results, four of which were players.
The situation is likely to lead to pressure on the Turkish Football Federation, which earlier this month set the resumption date for the Super Lig.
The Turkish FA has responded to its critics, who suggest the return plan is rushed, with a written statement emphasising that return dates are not irreversible and they are constantly in touch with public health authorities, carefully examining developments regarding the wellbeing of players, coaches, club officials and staff.
Football activities have been suspended in Turkey since March owing to the outbreak of coronavirus, which is still wreaking havoc around the world.
Despite the positive tests, a number of Super Lig teams, including Galatasaray, continued to train as normal today.
The race for the 2019-20 Super Lig title is finely poised, with the top four clubs separated by as many points with eight games of the season left to play.
Trabzonspor lead the way on 53 points, however with just goal difference keeping them ahead of Istanbul BB. Galatasaray are on 50 points, while Sivasspor have 49.
It is equally tight at the bottom of the table, with Genclerbirligi in 12th on 28 points, while bottom of the 18-team table are Kayseri on 22 points.
Such a tightly fought league would make any early conclusion to the campaign - whether declaring the season null and void such as in the Netherlands, or calling the winners and relegated sides as they are now, as in France - very controversial.