Many theories have been discussed by the media as to what the Italy defender said to incite the head butt attack from Zidane on his final game before retiring.

It is thought the comments may be related to Zidane's family. Zidane whose parents are Algerian immigrants, has endured taunts about his heritage throughout his career.

Materazzi has denied saying he insulted the Frenchman's mother or calling Zidane a "terrorist."

Regardless of Materazzi's statements FIFA has confirmed they will look into the incident.

"FIFA will open a disciplinary investigation into Zidane's conduct to enable it to clarify the circumstances surrounding the incident as exactly as possible," a FIFA statement said, as reported by Sky Sports.

If the Inter Milan player is found guilty of making any racist remarks to Zidane, he may suffer a long-term ban according to FIFA's strict anti-discrimination regualtions.

Zidane was red-carded for the offense and France went on to lose the final 5-3 on penalties.