COPENHAGEN, DENMARK -- Danish health officials have urged soccer fans who attended the European Championship game between Denmark and Belgium on June 17 to be checked for the coronavirus after they found at least three people who later tested positive for the delta variant.

Danish Health Minister Magnus Heunicke wrote on Twitter on Wednesday that about 4,000 people sat near those who tested positive.

All those who attended the three Euro 2020 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 allowed to attend the host team's game against Belgium as restrictions began to ease in the country.

The head of the Danish Agency for Patient Safety said the people were infected independently of each other and were infected during the game.

"They did not get symptoms until three or four days later, which means that there must have been some kind of unknown source of infection present in the section where they sat," Anette Lykke Petri told Danish broadcaster DR.

Denmark has reported 247 case of the variant since April 2. According to Danish media, the fans that tested positive were Danes.

Copenhagen will host one more match at Euro 2020 on Monday. Spain will face Croatia in the round of 16 in that game. Denmark will play its next game against Wales in Amsterdam on Saturday.

Heunicke said the Danish Patient Safety Authority and the Danish soccer federation "work closely together on effective infection detection."

The Danish Patient Safety Authority said there is no recommendation to go in isolation.