An Amsterdam-based nongovernmental organization (NGO) has filed an appeal against Dutch prosecutors for dropping charges against two shipbuilding companies accused of employing North Korean workers.

According to La Strada, the two Dutch companies — which it did not name — “are suspected to have acquired ships from Polish shipyards while being aware that these ships were constructed at wharves employing North Korean workers,” the NGO said in a written statement on Friday.

The NGO said these workers labored under “inhumane, exploitative conditions that are in clear violation of international labor laws.” But Dutch prosecutors dismissed the case last year due