Four people were detained after police made their largest ever seizure of heroin in Germany, prosecutors said on Friday, with police confiscating some 700 kilos as part of an operation against a gang smuggling narcotics from Iran.

The drugs were seized in the port city of Hamburg at the end of August. The detentions were made overnight on Thursday, when police searched 10 premises in the eastern cities of Dresden and Chemnitz, in Hamburg and in the Netherlands.

They seized documents, laptops, storage devices, smartphones and vehicles.

The detained were an unnamed 40-year-old Turkish-Serbian suspected ringleader, a 35-year-old Iranian in the Netherlands, a 54-year-old German suspected of using his firm’s logistics fleet to transport drugs, and a 53-year-old Turkish go-between.

One was detained in Germany, one in Spain, and two others in the Netherlands. Prosecutors are seeking the extraditions of the three who were arrested abroad, while a court in Dresden is due to decide on Friday whether the person detained in Germany should be placed under arrest.