Djokovic, who took the coronavirus test on Monday after returning to Belgrade from the Croatia leg of the event, is expected to announce the result later on Tuesday.
"This was the worst possible scenario," the event's director Djordje Djokovic told Serbia's Prva Television.
"Novak was not obliged to take the test in Croatia as he had no symptoms. He took the test straight after his flight landed in Belgrade.
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"Around 100 people were tested and I was hard-hit by news that some of them came back positive, especially my childhood friend Borna Coric. We wish all of them a speedy and painless recovery."
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Bulgarian Grigor Dimitrov pulled out of the tournament in Croatia's coastal resort of Zadar after feeling unwell following his match with Coric on Saturday.
He informed the organisers ahead of Sunday's final he had tested positive upon his return to his Monte Carlo residence, leading to the cancellation of the showdown between Djokovic and Russian Andrey Rublev.
Croatian Coric tested positive on Monday as did Serb Viktor Troicki, who did not take part in the Zadar leg of the Adria Tour but featured in the first leg staged at Novak Djokovic's tennis centre in Belgrade on June 13 and 14.
Djokovic's fitness coach Marco Panichi and Dimitrov's coach Christian Groh also tested positive.
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Djordje Djokovic said he had made the decision to cancel the Zadar final in order to contain the damage.
"We wanted to protect every player and fan after learning that Dimitrov tested positive. It was a charity event and all we wanted was to play tennis and give the fans a good show," he said.
A sellout 4,000 crowd attended both days of the Belgrade event and as many turned up to watch the Zadar event, with its Visnjik tennis complex half-full after Croatia's authorities ordered spectators to implement social distancing.
The third leg which was due in Montenegro on June 27 and 28 was scrapped during the Belgrade event amid coronavirus concerns voiced by the Montenegrin government.
The final leg scheduled for Bosnia's city Banja Luka on July 3 and 4 is likely to be cancelled, although the tour's organisers are yet to confirm its fate.
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