Sasco Tacs, 30, and a 20-year-old woman, Vesna Milosevic, were arrested last month following a raid on an apartment in Trieste, Mario Bo, head of the Trieste police department's criminal division, said on Monday. They were charged with trafficking in prohibited substances.
Trieste is a town in north-eastern Italy near the border with Slovenia.
The police investigation began after a post office in Trieste reported that US postal authorities in Iraq returned hundreds of packets of steroids and other performance-enhancing drugs because they were improperly addressed, Bo said.
The drugs had been ordered over the internet, and Italian officials presume that some had reached their destinations, police said. US military officials in Iraq had no immediate comment.
Italian police said the Slovenians also sent steroids to customers in Europe, North America and Australia.
They seized 215,000 doses of prohibited substances in the
raid, officials said, estimating the ring may have had as many as 1000 customers around the world.
Bo said Trieste authorities were ready to cooperate in any international investigation, but that they had not been approached by the US authorities.
The Italian newspaper Corriere della Sera said the authorities believe the Slovenians received orders for the drugs on three internet sites run by servers in Slovenia, Poland and Lithuania.
"They rented the Trieste apartment specifically as a centre to fulfil the orders," Bo said.
Eight Italians are under investigation as possible accomplices, police said. Italy has tough laws against the use of performance-enhancing drugs, with athletes risking prison terms if detected.