ROME (AP) — Police in Italy say they have arrested 19 people, most from Tanzania, as part of dismantling a heroin ring involving more than 150 suspects in Africa, Asia and Europe.

Carabinieri police said the arrests Saturday stem from a probe begun in 2012 with a heroin seizure in Perugia, a university town in central Italy.

Investigators say one ringleader is a Tanzanian who, from his base in Poland, directed heroin shipments from Asia to Italy for street sales.

Since the probe began, 144 drug couriers have been arrested.

Initially using Africans, traffickers later employed Italians, Greeks, Spaniards, Bulgarians and Hungarians as drug couriers.

Police say couriers reached Italy aboard cargo boats, planes, trains, buses and taxis.

Heroin worth 35 million euros ($39 million) and cocaine worth 4.2 million euros ($4.7 million) has been seized during the course of the probe.