Exclusive by Osasu Obayiuwana BBC Sport, Tunisia

Blatter wants the differing bans explained

In an exclusive interview with BBC Sport in Tunis, Fifa president Sepp Blatter said he wanted to know why the players - who tested positive for the steroid nandrolone - were given different sanctions by the Italian Football Federation.

Inter Milan striker Kallon, the Sierra Leone captain, was handed an eight-month ban.

But Perugia midfielder Gadaffi, a Libyan international, was given a shorter sentence of three months.

"The files regarding the two cases are with Fifa and we will examine them to see if they were handled in the right way," Blatter said.

Saying that they do not know where the substance came from is no excuse Fifa president Sepp Blatter

"We also want to know why there was a difference in sanctions regarding the two cases," Blatter said.

Kallon and Gadaffi have denied taking any substances that could have led to the positive tests that were conducted by the Italian Olympic Committee (CONI).

But Blatter insists both players must take responsibility for their actions.

"Saying that they do not know where the substance came from is no excuse.

"The laboratories are very clear when they make their tests," Blatter said.

He added: "You cannot say that they are mistaken or the tests were mislaid.

"Something happened to the players and I'm sure that it comes with the food and the additional vitamins they are taking," Blatter said.

The Fifa president warned players not to ingest food or dietary supplements without having full knowledge of their contents.

"Players have to be very careful, because you cannot have food or drinks without knowing their composition, which tells you if they contain something that could be detrimental to their health."

Blatter admitted that he had been "naive" about the presence of drugs in football and said the problem needed to be dealt with firmly.

"We had two cases at the World Youth Championship and this is an alarm for football.

"We must combat this problem and stamp drugs out of our game," the Fifa president said.