European Union police agency Europol said Thursday that an international operation has smashed a Balkan crime ring and seized more than 1 ton of cocaine transported from South America to Europe in private planes.

Europol said the Balkan drug traffickers used private planes to move cocaine between South America and Europe and shipped drugs to Hong Kong and Macao in Asia.

In May, 600 kilograms of cocaine were seized in the Swiss city of Basel, according to Europol and Swiss police.

Another 421 kilograms were seized in Hong Kong.

Europol said that two key members of the network were arrested in Switzerland and in Croatia, out of a total of 16 arrests that took place in these two countries as well as in the Czech Republic, Serbia and Hong Kong.

Police not only seized cocaine, but also 2 million euros ($2.2 million) in cash and 1 million euros of luxury goods such as watches and vehicles, during raids in Croatia, the Czech Republic, Serbia, Slovenia and Switzerland.

Croatian police launched the investigation in early 2018, which spread to include law enforcement authorities from South America, Asia and across Europe as well as country offices of the U.S. Drug Enforcement Administration, Europol and EU border agency Frontex.