A diplomat who worked at the Japanese Embassy in the Democratic Republic of Congo was arrested Monday on suspicion of setting a fire at the mission in June, police said.

Tokyo police nabbed Shinya Yamada, 30, third secretary at the embassy in Kinshasa, who had returned to Japan to work at the Foreign Ministry following the June 20 fire. No one was injured in the incident.

It is rare for Japanese investigative authorities to probe a case that occurred at a diplomatic mission abroad.