Dutch container ships brokers have been fined in a Dutch court for facilitating the smuggling of military cargo from China, the Netherlands’ foreign ministry said on Thursday.

Dutch Foreign Minister Frans Timmermans said the two men who were arrested for allegedly aiding the smuggling were among more than 1,000 people currently in prison in China.

He added that the investigation was ongoing and that the cases were being treated as a “national security matter”.

The two men were among the “more than 1.3 million tonnes of military supplies and military equipment” being smuggled from China to Europe by container ships in the past year, Timmerman said.

Dutch media reported that they were arrested in late November for aiding the military, the Associated Press news agency reported.

The Dutch foreign ministry confirmed the two arrested men, but declined to provide further details, saying it was a national security matter.

Last year, the European Union banned container ships from using military cargo and military cargo containers as a means of transport between countries and territories.