The government has succeeded in extracting samples of a next-generation resource called methane hydrate from the bottom of the Sea of Japan, the Agency for Natural Resources and Energy said Thursday.

Researchers conducted drilling surveys and were able to obtain samples of the "fiery ice" under the ocean floor off Niigata, Akita and Yamagata prefectures. The samples collected were up to a meter thick.

The agency, an arm of the Ministry of Economy, Trade and Industry, will continue its three-year survey on methane hydrate — a frozen substance consisting of methane and water — through fiscal 2015 and aims to assess the amount extant in the Sea of Japan.

The agency also said a sonic survey of some 20,000 sq. km Japan's coastal waters found geological structures — suggesting possible reserves of the natural gas — at 746 locations. That comes on top of 225 locations found earlier.

It is estimated that there is enough methane hydrate beneath coastal waters to meet the nation's natural gas needs for 100 years.

But technology to extract methane hydrate has yet to be fully developed. There are also concerns about environmental damage linked to extraction, partially because methane is a powerful greenhouse gas.