A British man has died in the Bulgarian capital of Sofia before England's Euro 2020 qualifier.
The Foreign and Commonwealth Office (FCO) said it was "supporting the family of a British man who died following an incident in Sofia".
Another British man suffered a minor injury in a separate incident, the FCO spokesperson said.
The announcement of the man's death came as England prepared to take on Bulgaria in Sofia on Monday night.
The FA said it would not be commenting until the full circumstances of both incidents were clarified.
Meanwhile, a statement on Bulgaria's Ministry of Interior said police officers in Sofia were called to help a 32-year-old "foreign national" at about 10:00 local time (08:00 BST).
"The police received a signal for a man in a helpless condition", it said, and he was taken to hospital.
"He suddenly began to act aggressively, raging and threatening."
The ministry said the man died while being taken to the Sofia Police Department and they would "work to clarify the circumstances of the incident continues".
England fans were involved in clashes with police in Prague on Friday, before their 2-1 defeat by the Czech Republic.