The Metropolitan Police Department arrested six people Wednesday including an executive of a Tokyo-based publisher on suspicion of violating the Pharmaceutical Affairs Law by advertising in books a type of mushroom as a treatment for cancer.

Police said the arrests are the first after the contents of a publication were determined to be ads for an unauthorized medicine.

The six include Yutaka Misawa, 58, president of health food distributor Misawa Kagaku, and Maki Kimura, 49, an executive at the publisher Shiki Shuppan.