Stoke are investigating reports of an incident at their training ground on Friday, the club announced. It has been reported that a pig's head was left in Kenwyne Jones' locker, and that the striker was furious on discovering it.
The Daily Telegraph website reported Jones smashed the windscreen of team-mate Glenn Whelan's car in retribution, believing he was responsible.
Stoke said in a statement: "The club takes seriously reports of an incident at our training ground this afternoon.
"A full internal investigation will be carried out and those responsible for any unacceptable behaviour will be dealt with in accordance with the club's disciplinary procedures.''