TOKYO 

Police in Japan have said that a 50-centimeter long drone with a miniature camera attached has been found on the roof of the prime minister's office, after apparently falling onto the roof from the sky.

Kyodo news agency reported an investigative source as saying Wednesday that a low level of radiation had been detected from the drone, which bore a radioactivity symbol.

"We don't think it poses any danger," it quoted a government source as saying. 

In Japan there are no laws regarding low-flying drones, and licenses are not required to fly them.