An England football fan is being questioned by police in connection with a fight that reportedly left a man in a coma, the Foreign Office said.
The incident happened in Italy before Friday night's match against San Marino.
Reports in Italy say that the 21-year-old man was arrested after the dispute broke out outside the Bounty pub in Bologna, 75 miles from the enclave republic of San Marino, where England won their Group H World Cup qualifier.
Local newspaper La Repubblica reported that a 65-year-old England fan was in a coma in hospital after undergoing major surgery for a head injury.
A Foreign Office spokeswoman said: "We can confirm the arrest of a British national in Italy on 21 March. We are providing consular assistance."
La Repubblica reported that a group of at least seven football fans, who had been drinking, started fighting outside the pub in the Via delle Moline.
They described the 65-year-old defending himself with a bar stool before being punched and then hitting his head on the ground as he fell.
England won the game 8-0 against the part-time minnows of San Marino at the Stadio di Serravalle, before Tuesday's crucial trip to Montenegro.