Two members of the Colombia delegation to Copa America tested positive for COVID-19 on Sunday, meaning three competing teams have players or officials infected before the tournament even kicks off. Eight Venezuela players tested positive on Saturday, as did three from Bolivia.

Host nation Brazil play the opening match against Venezuela on Sunday. The game in Brasilia will be followed by Colombia vs. Ecuador.

The news of more positive tests comes as CONMEBOL defends itself against accusations the tournament, which was awarded to Brazil with less than two weeks' notice, was cobbled together at the last minute. Brazil was picked after Colombia was withdrawn due to a wave of civil unrest and cohosts Argentina pulled out because of a surge in COVID-19 cases.

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"The decision to hold the Copa America in Brazil was not taken on a whim or improvised," CONMEBOL said in an open letter. "It wasn't put together at the last minute, which would be impossible."

The organisation said Brazil's experience in hosting international sporting events -- it staged the World Cup in 2014, the Olympics in 2016 and the last Copa America two years ago -- made it a logical choice, as did the fact that Brazil has hosted international soccer matches throughout most of the pandemic. It also defended hosting the tournament in a time when COVID-19 is still not under control in South America and vaccinations drives are in their infancy in most countries.

"The sanitary bubble the delegations are in is supposed to minimise contact with others outside it, the taking of tests 48 hours before each game by all the people involved in the matches and the transfer of delegations by charter plane" all help limit the virus's spread, CONMEBOL said.

Brazil's Supreme Court on Thursday rejected three injunctions sought to prevent the tournament being held in the country because of the coronavirus pandemic. Brazilian president Jair Bolsonaro, who has played down the severity of the coronavirus and fought against lockdowns, has supported the move to bring the Copa to his country.

The oldest international tournament in the world, the Copa America final is at the Maracana stadium in Rio de Janeiro on July 10.