A 26-year-old male student was arrested Tuesday on charges of violating the explosives control law after he was found in possession of what appeared to be homemade gunpowder while near the U.S. Embassy in Tokyo last month.

Before his arrest, Shogo Koyama, a university student from Suita, Osaka Prefecture, had been quoted as saying during voluntary questioning that he had "come to throw (explosives) into the embassy" after learning how to make the mixture online, according to investigative sources.

Koyama is suspected of placing around 160 grams of gunpowder into a cloth-wrapped cup and carrying it in his pocket while on the street in front the embassy around 9 p.m. on Aug. 8. He was stopped by a police officer on duty who noticed him acting suspiciously.

The public security bureau of the Metropolitan Police Department, which believes the suspect acted as a "lone wolf," is investigating his motives and how he came to possess the gunpowder.

The police have searched locations including the man's house in Osaka Prefecture in western Japan and seized what are believed to be ingredients needed to make gunpowder.

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