About 4.3 tons of cocaine worth $255.86 million were confiscated in Italy on Tuesday and are linked to the Colombian Clan del Golfo drugs gang.

The drug bust accounts for one of the largest ever in Europe and is a part of a yearlong investigation. The drugs were flown to Italy by undercover cops who passed them on to the Italian traffickers who were then arrested.

"The purchasing organizations were different and did not know that the cocaine had already been seized, the producer in Colombia had already been paid and did not know about the seizure," Colonel Leonardo Erre of the Trieste Guardia di Finanza police said during a press conference on Tuesday.

"And so thanks to front companies and undercover agents, we were able to run the operation, delivery after delivery for over a year until the end of May," he added.

Italian police have now issued arrest warrants for 38 people on suspicion of international drug trafficking in Italy, Slovenia, Croatia, Bulgaria, the Netherlands and Colombia.

The investigation involved officials from Italian financial police and was coordinated by anti-mafia investigators along with U.S. Homeland Security.

The anti-mafia investigators said in a statement that the drug bust “took another strong tackle to one of the most important groups of Colombian narcos.”

The bust was executed by undercover agents who infiltrated the drug smuggling chain with 19 “controlled deliveries.” This led to key traffickers being uncovered. Along with the cocaine, the Italian police also confiscated about $1.97 million in cash.

Drug trafficking was occurring in Veneto and Lombardy, the Lazio region including Rome and the southern region of Calabria.