text: A drone carrying small traces of a radioactive material landed on the roof of Japanese Prime Minister's office in protest against the government's nuclear energy plans. The police and bomb squad were called after the four-propeller, 50-centimeter wide drone, was spotted by member of the Prime Minister's staff, on the roof of his principle office and residence in Chiyoda-ku, Tokyo. The drone was equipped with a small camera and a plastic bottle containing small traces of a radioactive material, according to Japanese media. Radioactive: The drone, which landed on the roof of the Japanese Prime Minister's official residence, was found to contain traces of a radioactive substance . Alert: Police and security officers investigate an unidentified drone found on the rooftop of the Prime Minister's official residence in Tokyo . The radioactive material is likely caesium, a soft metal and harmless to the human body, Tokyo Metropolitan Police said. It is not known who flew the drone onto the building but it is widely suspected it was someone protesting against the country's nuclear policy. People in Japan have become increasingly wary about the number of nuclear power plants in the country, following the disaster at the Fukushima Daiichi nuclear power plant after the Tōhoku earthquake and tsunami in 2011. Flown in: The blue tarpaulin covering the drone can be seen next to the helicopter pad on the roof of the Prime Minister's office in Tokyo . Guarded: Police and the bomb squad were called in after a member of the Prime Minister's staff noticed the drone on the roof . Tests to determine whether to plant should be decommissioned are currently being carried out, though many are skeptical over whether it would happen. Meanwhile, the Japanese government reportedly plans to dump 30 million tonnes of radioactive debris from the disaster in a waste complex by nearby village, Okuma. Anti-nuclear protests were held outside the Kagoshima District Court to stop reactors at Kyushu Electric Power Co's Sendai nuclear-power station in Satsumasendai, southwest Japan from being restarted, amid fears they were at risk fro earthquakes and volcanic eruptions. Standing guard: A police officer outside Prime Minister Shinzo Abe's official residence in Tokyo . Investigations: Officers comb the roof for clues after a drone (pictured right) landed on top of the Prime Minister's official residence in Tokyo . Prime Minister Shinzo Abe was pushing for the reactors to be put back online as he wants to cut Japan's dependence on imported fossils fuels. The courts agreed, meaning they will be back online in less than two years. The drone was initially covered with a piece of cardboard and covered by blue tarpaulin before being removed. Mr Abe was not in residence at the time as he is currently in Indonesia attending the Asia-Africa conference in Jakarta. Chief cabinet secretary Yoshihide Suga said police were investigating Wednesday's incident and that the government may consider new regulations on drones.
target: Remote control device had miniscule levels of radioactive substance .
  Follows protests over plans to restart two nuclear reactors .
  Fears over nuclear policy stem from Fukushima disaster after tsunami .
  Prime Minister Shinzo Abe was not in residence at the time .