SAPPORO, March 27 (Kyodo) — Coal mines in Japan's northernmost main island Hokkaido, which had been struggling against an influx of cheap coal imports, have seen a resurgence in production amid rising demand for coal-fired power plants due to the suspension of nuclear reactors.

Whereas many major coal mines in Japan have disappeared after the fuel source was largely replaced by petroleum and less expensive coal imports, the Ishikari coal field in Hokkaido continues to operate, and has even produced its largest yield.

The increased demand has come as two out of the three reactors at Hokkaido Electric Power Co.'s Tomari nuclear power plant, which generates about 40 percent of electricity in Hokkaido, were shut down for a virtually indefinite period and the utility has subsequently operated its coal-fired power plants to make up for the lack of nuclear power.

The Ishikari coal field, which once boasted the biggest coal production capacity in Japan, stretches across Bibai, Yubari and several other towns and cities in central Hokkaido.

One of the mines in the field, the Nishimukizawa mine, continues to practice surface mining, a form of mining in which coal is extracted from the surface of coal beds, instead of through tunnels. Snow and soil are removed from the surface to reveal black coal layers, each several meters thick.

Takemi Ouchi, president of Bibai-based Sanbi Mining Co., which began operating the mine two years ago, said Hokkaido Electric asked the company to increase its production as much as possible shortly after the March 2011 earthquake and tsunami caused meltdowns at the Nos. 1 to 3 reactors of Tokyo Electric Power Co.'s Fukushima Daiichi nuclear power plant.

Following what has become the world's worst nuclear accident since the 1986 Chernobyl disaster, the Japanese government plans to reduce its reliance on nuclear power and has required utilities nationwide to go through disaster resilience tests.

Without a go-ahead from the government, the utilities are not allowed to restart any of the idled reactors. Out of Japan's 54 commercial reactors, 53 have been halted, leaving the No. 3 reactor at Hokkaido Electric's Tomari plant online. At the plant, the Nos. 1 and 2 reactors are idled and the No. 3 is also scheduled to be shut down for safety checks on May 5.

"We'd like to continue mining coal as long as orders are coming," Ouchi said.

Hokkaido Electric has also been sending electricity to other utilities on Honshu, the largest main island of Japan, since the Great East Japan Earthquake.