The Turkish Boxing Federation said two fighters and a coach tested positive since returning from the event.
Marko Marovic of the Croatian Boxing Federation also claims a fighter and two of its coaches have the disease.
He told BBC Sport: "Our epidemiologist says they were most probably infected during [the] Tokyo 2020 qualifier."
Marovic, secretary general of the Croatian Boxing Federation, added: "Our first concern is the health of our boxing family. We are still praying that everything ends well and there will be no other positive tests."
