Kanagawa Prefectural Police on Wednesday arrested a former prefectural assembly member for alleged possession of illegal stimulant drugs.

Koichi Yokoyama, 41, who belonged to the Liberal Democratic Party until his resignation earlier this month, is suspected of possessing powder that contains outlawed substances. Police searched his home in Yokohama on June 26, on a tip from a female acquaintance, NHK reported.

On June 30, he submitted a letter of resignation to the Kanagawa Prefectural Assembly. His letter was accepted and his resignation became official on July 8, according to the assembly secretariat.

In 2012, Yokoyama was among the assembly members who submitted a petition calling for tougher government measures on so-called "dappo" (law-evading) drugs, usually a mix of dried herbs and synthetic stimulants, which are known to cause hallucinations and euphoria.