NHK has learned that a man in Sapporo City, northern Japan, was referred to prosecutors for allegedly producing handmade weapons illegally. He was quoted as saying that he rushed to buy more materials following the fatal shooting of former Prime Minister Shinzo Abe, expecting tighter regulations.

Investigative sources say Suwa Hironobu, a 29-year-old former office worker, was arrested last year on suspicion of possessing black gunpowder in his home. He has already been indicted on the charges.

The sources say a gun made from steel pipes and three sets of handmade explosives were seized from his apartment.

Police later confirmed the gun was lethal. They also identified the explosives as HMTD, a chemical compound that had been used in terror incidents overseas.

The police sent the case to prosecutors again on Wednesday for suspected violations of laws on weapons manufacturing, explosives control and others.

The investigators say the suspect apparently started making these weapons last spring.

He has reportedly admitted to most of the charges. The suspect also said he built the gun and explosives in order to commit suicide.

He allegedly told interrogators that his gun is more lethal than the one used in Abe's shooting.

The investigators say it appears unlikely that any homemade weapons fell into the hands of a third party.

The police are continuing their investigation to determine facts such as where the suspect acquired the materials for these weapons.