A paper bomb which went off and injured nine people at yesterday's Turin derby may have been produced by fans of home side Torino and not Juventus as originally believed, Italian authorities said on Monday.

Serie A's disciplinary tribunal said it had postponed a decision on possible sanctions after consultations with the government's agency for security at sports events (ONMS).

The tribunal said in a statement that its own observers had said the bomb was thrown from the area occupied by Juventus supporters.

However, it quoted an ONMS report as saying that "careful investigations are under way to ascertain whether the bomb which went off in the Torino sector was launched from the Juventus sector or had been produced and detonated by the Torino fans themselves."

Police said nine people were injured when the bomb went off in the Torino sector before the derby, which the home side won 2-1.

Violence also flared before the game when 300 Torino fans tried to block the Juventus team bus from entering the stadium compound and threw stones at the vehicle, breaking one of its windows.

Two Juventus fans and one Torino supporter were arrested over the incident during the match and a further two Juventus fans were detained in relation to disturbances outside the stadium.

"This can't go on like this, I'm tired of it," Giovanni Malago, president of the Italian Olympic Committee (CONI) told Italian media.

"Every weekend ... you end up getting suffocated by what happens on the football field. And this is despite the remedies and the efforts of the last months."

Sampdoria said on their official website that ticket sales had been suspended for Saturday's match at home to Juventus, pending a decision from the ONMS.