Japanese police arrested Saturday a man who admitted to flying a small drone carrying radioactive sand from Fukushima to the prime minister’s office in protest of the government’s promotion of nuclear power.

Yasuo Yamamoto, 40, turned himself into police in western Fukui prefecture Friday evening and was arrested on suspicion of forcible obstruction of business and interfering with the operations of the premier’s office, Kyodo News reported.

A drone bearing a radioactivity symbol with a miniature camera attached was found on the roof of Prime Minister Shinzo Abe’s office Wednesday.

According to Anadolu Agency, The resident of Obama city, which houses more than a dozen nuclear plants, reportedly told police that the 50-centimeter drone had been carrying a plastic bottle that contained sand from Fukushima, a coastal prefecture where a 2011 earthquake-tsunami triggered a nuclear disaster.

Kyodo cited investigative sources as saying Tokyo police had confirmed that radioactive cesium had been detected in the container, and that the drone had a global positioning system that — when operational — records its flight path.

Yamamoto had reportedly appeared with sand and what appeared to be a drone controller.

He said he had flown the device on April 9 and had written blog posts regarding flying a drone, which detailed his one-day round-trip from Obama to a parking area in Akasaka, central Tokyo.

In the wake of the drone’s discovery, the government has started mulling regulations on the flight of such devices above important facilities, with Kyodo quoting Chief Cabinet Secretary Yoshihide Suga as saying Friday, “we need to immediately establish” legislation on drone usage.

He said such devices “could have a substantial impact on public safety and privacy protection, depending on how they are used.”

Earlier this month, the Fukui District Court issued an injunction ordering a power supplier not to restart two reactors near the coast that had cleared the safety screening of the country’s nuclear regulation watchdog.

Following the 2011 nuclear crisis, all commercial reactors in the earthquake-prone country have remained offline since September 2013 until their clearance in the Nuclear Regulation Authority’s safety review.

Abe has been pushing for the revival of the nuclear power industry, a controversial issue due to safety concerns among the public.

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