Police in western Japan have reportedly found what appear to be metal nuts at the site where an explosive device was hurled toward Prime Minister Kishida Fumio during an election campaign appearance.

Wakayama prefectural police suspect that a man under arrest in the attack added metal nuts to the device to cause greater damage.

The incident occurred at a fishing port in Wakayama City last Saturday, when Kishida was about to give a campaign speech.

Kishida was unharmed, but two people suffered minor injuries when the cylinder-shaped explosive device detonated.

Police arrested 24-year-old Kimura Ryuji on the spot.

Investigative sources say on-site investigations discovered multiple objects that looked like metal nuts.

Footage of the incident also shows what appear to be nuts attached to the outside of another cylinder the suspect was holding when he was pinned down.

The cylinders, or pipes, were likely filled with gunpowder and had caps on both ends. Police suspect that Kimura attached the metal nuts to cause greater damage when the device exploded.