A Chiba police officer sustained minor burns to his face and hands when a police box men's room he was using exploded when he lit his lighter.

It's thought the washroom was filled with gas from a natural gas pocket that had leaked into the drain pipe.

The site of the explosion is in the center of the Boso Peninsula, the location of the first natural gas well in Japan. The region has seen a number of explosions believed to have been caused by natural gas.