Danish health officials say they have recorded five cases of the COVID-19 Delta variant after the country's Euro 2020 match with Belgium.
Authorities have urged any supporters who attended the game on June 17 in Copenhagen to be tested for the coronavirus.
Danish Health Minister Magnus Heunicke said on Twitter that about 4,000 people had sat near the five people who have tested positive for the variant, in six specific stadium blocks.
The head of the Danish Agency for Patient Safety said the individuals were infected independently of each other and caught the variant during the game.
The agency has "worked closely on effective infection detection," with Denmark's football federation, Heuncike added.
Meanwhile, two other positive cases of coronavirus were recorded after Denmark's game against Russia on Monday.
"I don't know which variant it is, but again that's a match where people are sitting very close together," said Thomas Rydahl, the head of the safety and security services for the games in Copenhagen.
Denmark has reported 247 cases of the Delta variant -- first detected in India -- since April 2. According to Danish media, the fans that tested positive were Danes.
All supporters who attended the three European Championship games in Copenhagen had to provide valid documents showing they were not infected with COVID-19 before being allowed to enter Parken Stadium.
About 25,000 fans were permitted to watch the host team's game against Belgium as Denmark began to ease its restrictions.
Copenhagen is due to host one knockout stage game at EURO 2020, as Spain plays Croatia on Monday.
The European Centre for Disease Control and Prevention has warned that the Delta variant of COVID-19 could account for 90% of new infections in Europe by late August.