A North Korean worker who claims he is a victim of modern slavery in a Polish shipyard has filed a criminal complaint against a Dutch shipbuilder that bought products from the Polish firm, an activist group said Thursday.

The Global Legal Action Network said in a statement that the man “endured 12-hour workdays in unsafe conditions and had much of his wages seized by the North Korean state.”

The network did not release the plaintiff’s name “to protect his safety.”

Dutch lawyer Barbara van Straaten, who filed the case Monday on the worker’s behalf, also is not revealing the name of the Dutch shipbuilder so as not to jeopardize a requested criminal investigation. Under Dutch law, companies can face prosecution if they profit from labor exploitation, even if it happened in another country.

The Global Legal Action Network said the North Korean worked at a shipyard in Gdynia, Poland owned by a private company, Crist. Company spokesman Tomasz Wrzask said the shipyard previously worked with a Polish firm called ARMEX that once employed North Koreans, but ended the collaboration in the summer of 2016.

ARMEX “had all the necessary permissions to operate in the European Union and in Poland, and was under the supervision of Poland’s National Labor Inspectorate. We had no reason for suspicion,” Wrzask said.

Wrzask said it was an “outrage” that Crist’s name was made public while the Dutch shipbuilder was not identified.

“The allegations were made without letting us know when the work was taking place, what was the project and what was the name of the Dutch company,” he said. “Without that, we cannot verify at this stage if it is connected with us”.

Global Legal Action Network Director Gearoid O Cuinn said the case “will send a strong message to multinational corporations that profiting from forced labor will entail serious legal risk.”

A Global Slavery Index published in July estimated that 40.3 million people worldwide were subjected to modern slavery in 2016. The Walk Free Foundation’s index reported that where one in 10 people lived under such conditions in North Korea, the highest concentration in the world.

The North Korean government also sends tens of thousands of workers abroad under arrangements that bring in revenue estimated at between $200 million to $500 million a year.