The World Cup Qualifier between Brazil and Argentina on Sunday night was suspended after Brazilian health officials entered the pitch in a row over Covid rules.
The officials marched onto the field shortly after kick-off and confronted the Argentina players, who left the field while the two managers - along with Argentina captain Lionel Messi and Brazil's players - gathered to discuss the stoppage.
The South American football confederation CONMEBOL later confirmed the game - which was 0-0 when it was stopped - had been called off by the referee, who they said would submit a disciplinary report to FIFA.
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A FIFA spokesperson said: "FIFA regrets the scenes preceding the suspension of the match between Brazil and Argentina for the CONMEBOL qualifiers of the FIFA World Cup 2022 which prevented millions of fans from enjoying a match between two of the most important football nations in the world.
"The first match official reports have been sent to FIFA. This information will be analysed by the competent disciplinary bodies and a decision will be taken in due course."
Antonio Barra Torres, the president of Brazil's health agency Anvisa, said four Argentina players will be fined and deported for allegedly not following the country's Covid protocols.
How Brazil vs Argentina abandonment unfolded
- 6pm: Brazil's health regulator Anvisa seeks the immediate isolation of four Argentina players just hours before they are due to face Brazil in a World Cup qualifier in Sao Paulo.
- 8pm: Brazil vs Argentina kicks-off as planned.
- 8:06pm: Play is halted as health officials walk onto the pitch to seemingly try and remove Emiliano Martinez of Aston Villa and Giovani Lo Celso and Cristian Romero of Tottenham from the pitch.
- 8:11pm: The game is suspended as Argentina players head back to the dressing room.
- 8:18pm: Lionel Messi appears to try and negotiate with the authorities but his team-mates remain in the dressing room.
- 8.40pm: Reports suggest a bus is en route to escort the Argentina team away from the stadium.
- 8:50pm: The game is abandoned.
What were the Covid protocols and were they broken?
Under Brazilian rules, visitors who have been in the UK in the 14 days before entering the country must quarantine for 14 days on arrival.
Although Anvisa did not name the four, the players with Premier League clubs are Emiliano Buendia and Emiliano Martinez of Aston Villa and Giovani Lo Celso and Cristian Romero of Tottenham.
Martinez, Lo Celso and Romero were named in Argentina's starting line-up, while Buendia did not make the squad.
On Monday, the Argentina national side's Twitter account posted a picture of several members of the squad on a plane with the caption: "We are going home!".
But Anvisa had sought the immediate isolation of the four players just hours before the game in Sao Paulo.
"Anvisa considers the situation a serious health risk and so has asked local health authorities to determine the immediate quarantine of the players, who are stopped from participating in any activity and should be prevented from remaining on Brazilian soil," Anvisa said in a statement ahead of kick-off.
The Argentine squad flew into Brazil on Friday, the day after beating Venezuela 3-1 in a World Cup Qualifier in Caracas.
Anvisa were tipped off the four players did not state they had been in the UK within the last two weeks on their immigration forms. The health regulator confirmed the details the players gave were "false".
The Argentine Football Association (AFA) expressed its "deep discomfort" at the suspension of the match.
It said the team had been in Brazil since September 3 and had complied with all the health protocols.
"Football should not experience these kinds of episodes that undermine the sportsmanship of such an important competition," the AFA said in a statement.
The Brazilian Football Confederation (CBF) said it "deeply regrets" the events that ended up causing the suspension and insisted Anvisa "could have exercised its activity in a much more appropriate manner in the various moments and days prior to the match".
It added: "The CBF also emphasizes that at no time, through the interim president, Ednaldo Rodrigues, or its directors, interfered in any point related to the sanitary protocol established by the Brazilian authorities for the entry of people into the country.
"The role of the CBF was always in an attempt to promote understanding between the entities involved so that the sanitary protocols could be fulfilled satisfactorily and the game could be played."
Argentina boss defends players
Argentina manager Lionel Scaloni insisted his side were not informed they could not take the field, telling reporters after the game: "I've come here so that our country can find out what's happened. It makes me very sad.
"I'm not looking to find any guilty parties. Whether something happened or not, it wasn't the right time for that intervention.
"It should've been a footballing spectacle for everyone to enjoy the best players in the world. I'd like the Argentine people to understand that as the national team coach, I have to defend my players.
"At no point were we notified that they couldn't play. We wanted to play the game, as did the Brazil players."
Argentine FA president Claudio Tapia added his players had not lied about being in the UK before entering Brazil, saying: "There can't be any talk of lies here because there is health legislation under which all South American competitions are played.
"Health authorities in every country approved a protocol that we have been fully compliant with.
"What's happened today is terrible for football and sends out a very bad image. Four people interrupted the game to inform us of something and CONMEBOL asked the players to go to the dressing room."
Anger in South America after chaos
The suspension of the match comes amid continuing anger in South America at rules which have prevented several teams from using key players for this month's three World Cup qualifiers.
Brazil were without nine key men for the Argentina game, and other South American sides have also lost players due to a decision by some European clubs not to let their players travel to the continent.
They would have to quarantine on return and the clubs do not want to lose their players for subsequent league games.
Aston Villa said Martinez and Buendia had agreed to return to the club after the Brazil game and miss Argentina's match against Bolivia on Tuesday. The Argentine Football Association, however, said they would play all three games.
Brazil and Argentina now await FIFA's next move after an extraordinary night.
Analysis: Could Brazil be handed win?
South American reporter Tim Vickery:
"The problem here is trying to fit everything in the calendar. They went ahead with the Copa America - an extra Copa America in June and July - and the problems to come were obvious.
"You'll remember that some of the players and some of the coaches made it clear that they were playing that Copa America under protest, not only because of the pandemic but also because they felt that time would be better employed catching up on World Cup qualification.
"As it stands, we've tried to fit three litres into a bottle that only holds two. Something had to give and it's given today in Sao Paulo.
"It's a very, very awkward one for FIFA because what happened is not European clubs versus South American national teams. This is an internal problem of how the pandemic is being handled and the rules in South America, specifically in Brazil.
"What the health officials here have done is uphold the rules and they are saying the Argentines gave false information when they arrived in the country.
"These are serious matters so this is very, very difficult for FIFA because this extrapolates football and with the calendar at the moment so crowded, it's not easy to work out if this game will go ahead.
"Will it be awarded to Brazil on a walkover? If it is going to be rescheduled, when is it going to be rescheduled? This is a real headache for the game's administrators."