Italian police said on Tuesday they had broken up a criminal network that smuggled mostly Syrian refugees across the Balkans to Western Europe.

International police forces arrested 21 people in Austria, Germany, and Italy on suspicion of people smuggling, a police statement said. The arrests followed an investigation conducted by prosecutors in the northern Italian city of Como.

Most of those arrested were Syrian, while others were Algerian, Egyptian, Lebanese and Tunisian and were officially resident in the area around Como, Italy.

The criminal group organized transport for more than 200 migrants from 2014 to 2016, charging at least 500 euros ($560) each, according to prosecutors, who worked together with the EU’s judicial cooperation unit, Eurojust.