An employee for Fenerbahce tested positive for the new coronavirus on May 7, forcing the Turkish Super Lig club to cancel training on May 8.
The Istanbul club tested all football players, technical staff and club personnel but results showed someone working at the team's premises was positive for COVID-19.
Another employee is suspected of having the virus.
Spor Toto Super League giant Fenerbahçe has dropped to the relegation zone, further increasing the pressure on caretaker coach Erwin Koeman and club president Ali Koç.
Istanbul clubs got the better of their opponents from Greece in the Euroleague this week, as Olympiakos lost at home to Fenerbahce on Thursday and Panathinaikos went down at Anadolu Efes on Friday.
The Reds suffered their third defeat in a row losing 73-72 in Piraeus to Fener that had Greek international Costas Sloukas score 20 points to decide the game in the visitors' favor.
Ali Koç, President of Fenerbahçe, helped carrying the coffin during the funeral ceremony at the stadium.
Spor Toto Super League leader Başakşehir will play city rival Fenerbahçe at home this weekend in a game that could reshape the race for the Turkish title.
Beaten by Sevilla in the UEFA Champions League play-offs, Turkey's Başakşehir will make its UEFA Europa League group stage debut this season against Bulgaria's Ludogorets as Konyaspor visits Marseille.
Başakşehir, the runner-up in last season's domestic title race, is highly motivated after it won 3-2 against city rival Fenerbahçe away, a first in its short history.
Defending champion Beşiktaş made a winning start to the new Spor Toto Super League season by beating Antalyaspor 2-0, while city rival Fenerbahçe was held to a 2-2 draw at newcomer Göztepe over the weekend.
Another newcomer, Malatyaspor, made its debut on the top flight with a 3-1 victory over Osmanlıspor on Aug. 13, while Alanyaspor lost 3-1 at home to Kasımpaşa on Aug. 12.