A man arrested for landing a drone with radioactive sand on top of the prime minister's office might have targeted a U.S. diplomatic housing facility in Tokyo for the stunt and tried to film a nuclear power plant in Kagoshima as well, sources close to the matter said Monday.

Yasuo Yamamoto, 40, who was arrested Saturday on suspicion of obstructing duties at the prime minister's office by landing a drone with a slightly radioactive payload on top of it, has said he did it to protest Japan's use of nuclear power, police said, adding they are investigating his plans for other attempted fights.

According to a blog posts written by Yamamoto, a resident of Obama, Fukui Prefecture, which hosts several nuclear power plants, he used a drone to take close look at Kyushu Electric Power Co.'s Sendai nuclear power plant in Kagoshima Prefecture last October.