MADRID (AP) — Police in Spain have arrested 12 people and seized about 600 kilograms of cocaine in an operation that dismantled what investigators describe as the largest drug distribution network in the country’s capital, authorities said Sunday.

The alleged drug trafficking gang funded the smuggling of Colombian cocaine and Moroccan hashish by selling in the Netherlands and central Europe large crops of marijuana purchased from growers across Spain, the National Police said.

It said that Colombia’s National Police helped in the investigation.

The leaders of the alleged drug trafficking network were a Moroccan man and two of his siblings, police said. One of them allegedly supervised the logistics of the smuggling and distribution of drugs while the other one acted as a frontman.

The trio were aided by other relatives and associates, including a lawyer who police said laundered the group’s earnings and took part in some drug sales.

Police investigators described the gang as "sophisticated," having a setup that allowed them to dispatch “huge drug quantities" of drugs under “dexterous security” conditions, including drivers transporting the drugs who wore suits to pretend they were businesspeople.

Instead of the usual way of selling the cocaine by the kilogram, police said that the gang found an easier way of distribution by dividing it into packages of 370 to 390 grams, which were sold for around 10,000 euros ($11,950) each.

Authorities impounded 16 apartments, 700,000 euros (around $835,000) in cash, 20 vehicles and several firearms and knives that belonged to the alleged drug traffickers.