The shutdown of a key thermal power plant may mean Hokkaido could see its electricity supplies reduced for over a week, a state minister said Thursday, following a powerful earthquake that rattled the island early that morning.

Efforts to restart the Tomato Atsuma power station in the town of Atsuma have been hampered by infrastructure damage and a fire at the plant after the magnitude 6.7 quake struck.

With the coal-fired power plant that provides roughly half of Hokkaido's electricity offline, around 2.95 million households served by Hokkaido Electric Power Co. experienced blackouts Thursday. The government said later in the day that supplies had been restored to about 340,000 homes.