Kallon joined Inter Milan in 2001
The Italian Olympic Committee (Coni) has announced that Inter Milan striker Mohamed Kallon has tested positive for two metabolites of the banned steroid nandrolone.
Coni said the positive test resulted from a sample given by the Sierra Leone international after Inter's 0-0 league draw at Udinese on 27 September.
Only Kallon's A sample tested positive and a test is yet to be carried out on his B sample.
Kallon now faces a suspension pending the second test.
Under new regulations in Italy, the player must decide whether he wishes a test to be taken on the B sample and it is expected that Kallon will do so.
The use of nandrolone has caused controversy in the past with a string of high-profile sports stars testing positive for the substance, which is found naturally in the body in small amounts.
Although nandrolone is a performance-enhancing stimulant, there are concerns that positive tests can be produced without an athlete knowingly taking the drug.
In football, Jaap Stam, Frank de Boer, Edgar Davids, Fernando Couto and Josep Guardiola have all received recent bans after testing positive for nandrolone.