The Kanto region alone is estimated to have over 400 billion cubic meters of natural gas reserves. It forms a Minami Kantō gas field in the area spanning Saitama, Tokyo, Kanagawa, Ibaraki, and Chiba prefectures. However, mining is strictly regulated in many areas because it is directly below Tokyo, and is only slightly mined in the Bōsō Peninsula. In Tokyo and Chiba Prefecture, there have been frequent accidents with natural gas that was released naturally from the Minami Kantō gas field.