
“We can confirm that a spectator fell from the stands just after kickoff in the match between England and Croatia at Wembley Stadium,” a stadium spokesman said.
“The spectator was given on-site medical attention and was then taken to hospital in a serious condition.”
Stadium officials said they will work alongside European football’s governing body Uefa to investigate the incident.
A crowd of 18,497 watched the match at Wembley.
The stadium will host eight matches during the tournament. It has a current limit of 22,500 fans – a quarter of its capacity – but there are hopes that both semifinals and the final could be played out in front of larger numbers.