A drone marked with a radioactive symbol and equipped with a water bottle containing radioactive material landed on the roof of the Japanese Prime Minister's office on Wednesday morning, police said. The drone carried trace amounts of cesium - a soft metal - but not enough to cause harm to humans.

Since Japan’s power plants were shut down after the Fukushima nuclear meltdown in March 2011, Prime Minister Shinzo Abe has been striving to reboot Japan’s nuclear power industry. His campaign has been unpopular; 40% of the public oppose restarting the nuclear program, and only 24% support it. The same day the drone was found on the roof, the Kagoshima district court rejected a residents’ injunction against restarting the first two nuclear reactors scheduled to initiate the program - a victory for Abe.

Drone technology has been the subject of a number of high-profile cases in the last year. Several drones were observed hovering over nuclear power plants in both France and Belgium, and their origins still remain a mystery. In February, a drone landed on the lawn of the White House. While the drone caused quite a security scare, it was never intended to reach the White House and was accidental according the drone’s operator.