WINONA — It didn’t take long for Winona police to make their first arrest under a new Minnesota law banning a synthetic drug known as “plant food.”

Officers arrested a 20-year-old Winona man less than an hour and a half after the law went into effect.

Deputy Police Chief Tom Williams said officers were called at 1:21 a.m. Friday about a man who had wandered into a home and was acting erratically.

Police arrived to find the man had locked himself in a bathroom. Once officers got into the room they discovered he was naked.

Police recovered his clothes and a container with a substance that tested positive for mephedrone, also known as plant food.

The man is in jail. The new law took effect at 12:01 a.m. Friday.