England fan 'had part of his ear bitten off'
The incident apparently took place during England's 2-1 Group D defeat to Uruguay, according to a statement attributed to the Association of Chief Police Officers.
"In the immediate aftermath, we managed to make contact with the victim and offered advice and support," read a statement widely reported in the British media.
"The day after the attack, the victim chose to make a formal complaint to the local police, and they opened an investigation.
"During the course of our pursuit of the assailant, we located and interviewed several witnesses.
"They were very helpful in giving their version of events, but, unfortunately they were unable to give us a name for the alleged attacker."
England lost the match to effectively end their hopes of progressing to the last 16 of the tournament in Brazil.
Two goals from Luis Suarez denied them, with the Liverpool striker subsequently involved in an alleged biting incident of his own when he appeared to sink his teeth into the arm of Italy's Giorgio Chiellini in his country's final group match.