Rally Cycling told Cyclingnews that all the rest of the group tested negative in follow-up tests on Friday morning but the US-registered ProTeam decided to withdraw from the race.
The team did not identify the person involved. It is unclear if any of the team will be declared close contacts and so be obliged to stay in Turkey for a period of isolation.
"We had a positive test with one of our team members overnight here at the Tour of Turkey,” Rally Cycling director Pat McCarty said.
"Follow-up tests with the rest of our group were all negative this morning. We made the decision to withdrawal ourselves from competition out of respect for the rest of the teams and staff working the race."
Rally Cycling took their first win of 2021 on stage 1 of the Tour of Turkey, with Dutchman Arvid de Kleijn beating the likes of Mark Cavendish, Jasper Philipsen and André Greipel. De Kleijn went on to take two fourth places in other sprint stages.
A number of riders and teams have withdrawn from races due to COVID-19 cases so far this season.
Swiss rider Simon Pellaud (Androni Giocattoli-Sidermec) was unable to start the Tour of Turkey on Sunday after testing positive for COVID-19 in pre-race testing. He was negative in a test on Thursday and is expected to travel home to Switzerland today.
Trek-Segafredo withdrew from Gent-Wevelgem after positive COVID-19 tests, while Bora-Hansgrohe were unable to ride the E3 Saxo Bank Classic as a result of a positive COVID-19 pre-race test by rider Matthew Walls, and also missed Gent-Wevelgem.
Under the strict UCI medical protocol created to limit the impact of the COVID-19 virus and ensure racing can be held, riders and teams have to form protective bubbles and undergo regular and pre-race testing. Contact with fans, the media and anyone outside of the bubble is strictly controlled.
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