Shizuoka Prefectural Police on Wednesday arrested a 40-year-old man of Fuji, Shizuoka Prefecture, his 41-year-old wife and 15-year-old son on suspicion of using a stimulant drug.

The police said they arrested the man and his wife, whose names were not disclosed, because their urine tested positive for the illegal drug described as a kakuseizai stimulant, which is believed to be either amphetamine or methamphetamine. Their son, who grauduated from junior high school earlier this month, also underwent a urine test and tested positive, they said.

They are suspected of using the drug between mid-March and Wednesday. The drug was not found in their house, and the police are investigating to determine how they obtained it.