A nuclear power station in Hokkaido is relying on emergency backup power after a powerful earthquake knocked out electricity on the northern island Thursday, offering a stark reminder of the 2011 Fukushima disaster.

The three-reactor Tomari nuclear plant, operated by Hokkaido Electric Power Co. and in shutdown since the aftermath of the Fukushima disaster, lost power after a magnitude 6.7 quake hit the island in the early hours, the government said.

The plant’s fuel rods are being cooled with emergency power supplied by diesel generators, Chief Cabinet Secretary Yoshihide Suga told reporters Thursday.

There were no radiation irregularities at the plant, Suga said, citing the operator.

The atomic regulator said the diesel generators have enough fuel to last seven days.

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Hokkaido Electric has shut down all fossil fuel plants, cutting power to all its nearly 3 million customers, a spokesman said.

Industry minister Hiroshige Seko has instructed Hokkaido Electric to restart its biggest coal plant after the station was tripped by the earthquake.

The blackout shut down Hokkaido’s New Chitose Airport, a popular gateway to the island, making it the second major airport to be knocked out in the country in two days after a typhoon swamped Kansai International Airport, the nation’s third biggest.

The March 11, 2011, magnitude 9 earthquake that struck off the northern Honshu coast set off a massive tsunami that devastated a wide swath of the Pacific coastline and left nearly 20,000 dead.

The quake knocked out power to the Fukushima No. 1 nuclear power plant, and the tsunami swamped diesel generators placed low in reactor buildings, leading to a series of explosions and meltdowns in the world’s worst nuclear disaster for 25 years.

The crisis led to the shutdown of the country’s nuclear industry, once the world’s third biggest. Seven reactors have come back online after a protracted relicensing process.

The majority of Japanese remain opposed to nuclear power after Fukushima highlighted failings in regulation and operational procedures in the industry.