The Natural Resources and Energy Agency said it visually confirmed that methane hydrate, a next-generation energy source, exists under the Sea of Japan off Niigata Prefecture.

The discovery, announced Friday, raises hope that more methane hydrate deposits may be found in other areas of the seabed with similar geological features off Niigata and Ishikawa prefectures, an official of the agency said.

Field surveys have identified more than 220 such potential spots in the Sea of Japan, the official said.

“We have made the first step toward confirming the amount of the resource, a key step toward the commercial production of a type of methane hydrate existing in the layer of the seabed near the surface,” he said.

But the official also said the agency cannot determine yet whether there is enough methane hydrate for commercialization, while the impact on the marine environment of developing the resource would also have to be taken into account before any such operations commenced.

Methane hydrate, an ice-like substance consisting of methane and water that is stable at low temperature and under high pressure, could become a critical source of energy for resource-poor Japan.

The nation succeeded in extracting natural gas from methane hydrate in geologic layers hundreds of meters below the seafloor of the Pacific in March, but exploration in the Sea of Japan has lagged because the resource exists in a form that is more difficult to extract.

Through a series of surveys conducted in June and July, 225 locations in the Sea of Japan off Niigata and Ishikawa were found to have geological structures with possible reserves of methane hydrate near the top layer.

Of these areas, the agency visually confirmed that white methane hydrate exists in one location around 900 meters below the water by using an unmanned vehicle equipped with a camera.

It plans to further check the thickness of the methane hydrate layer and the density of the substance to estimate the amount. At the same time, it will also investigate other parts of the Sea of Japan seabed, including areas off the coast of Akita and Yamagata prefectures.