Aerial footage shows large areas of Atsuma in Hokkaido hit by landslides on Sept. 6 following an earthquake measuring a maximum 7 on the Japanese intensity scale that struck at 3:08 a.m. (Video footage by Takahiro Kumakura)

A maximum-intensity earthquake struck southwestern Hokkaido early on Sept. 6, killing at least 7 people, destroying buildings. triggering landslides that buried houses, and cutting off electricity to all homes on the main northern island.

The magnitude-6.7 quake hit at 3:08 a.m. with the epicenter located in the eastern Iburi district that stretches along the southwestern coast.

Chief Cabinet Secretary Yoshihide Suga said at his afternoon news conference that seven deaths have been confirmed: four in Atsuma; one in Sapporo; one in Mukawa; and one in Shinhidaka.

Around 30 residents were missing in Atsuma, where landslides smashed into houses in the town, and at least nine residents might be buried in their homes, Atsuma government officials said earlier.

Hokkaido the previous day was hit by Typhoon No. 21, and the heavy rainfall loosened soil on hills and mountains.

In Tomakomai, an 82-year-old man was showing no vital signs after he fell down stairs at his home.

An additional 94 people were reportedly injured in the quake, but the extent of their injuries was not immediately known.

The top intensity of the quake was initially listed as an upper 6 on the Japanese seismic scale. But around 3:30 p.m. on Sept. 6, the Japan Meteorological Agency (JMA) said the intensity in Atsuma reached the maximum of 7, making it the first such quake to strike Hokkaido.

JMA officials warned that strong aftershocks could continue for a week.

In the immediate aftermath of the quake, the JMA was unable to obtain intensity readings from a number of meters in the area closest to the epicenter, including in Atsuma, through its ordinary communication lines.

However, on the afternoon of Sept. 6, those lines came back online, leading to the confirmation of the intensity data.

Data from other points were also obtained, showing an upper 6 intensity in Mukawa, lower 6 readings in Hidaka and Biratori, and upper 5 levels in Niikappu and Shinhidaka.

JMA officials were still waiting for data from a number of other seismic meters.

The earthquake also caused a chain reaction that led to a power outage at all 2.95 million households in Hokkaido, officials of Hokkaido Electric Power Co. said.

The utility explained that a coal-fired thermal plant in Atsuma, the largest in Hokkaido, was heavily damaged in the earthquake. The suspension of operations there caused an imbalance in the supply and demand for electricity. As a result, operations were stopped at all other thermal plants in Hokkaido.

The power outage was the first to affect the entire island.

One of the coal-fired thermal power units at the Sunagawa plant in central Hokkaido resumed operations around 2 p.m., according to Hokkaido Electric Power officials. Electricity returned to some households in Asahikawa, but the utility still has a long way to go before restoring power to the entire island.

The Sunagawa plant unit that was restarted has an output equivalent to only 3 percent of peak electricity demand in Hokkaido.

Hokkaido Electric Power officials also said they were working to start up a hydroelectric plant to resume supplying electricity.

Hiroshige Seko, the industry minister, said he expected it would take at least a week before electricity could be restored to all of Hokkaido.

Officials of Hokkaido Electric Power and the Nuclear Regulation Authority said the quake also severed all outside power sources to the Tomari nuclear power plant in Tomari, Hokkaido. But all three reactors were not operating at the time.

Six emergency diesel generators were being used to cool spent nuclear fuel stored in a pool at the plant. Officials said the plant had enough fuel to operate the diesel generator for at least seven days.

Officials said no other problems were found at the Tomari nuclear plant, and radiation levels were normal.

Transportations systems were in turmoil following the earthquake.

Hokkaido Railway Co. suspended operations on all lines from the scheduled start of runs on the morning of Sept. 6. The railway company had no idea when operations would resume.

The subway and streetcar systems in Sapporo, Hokkaido’s capital, were also suspended because of the power outage.

The lack of electricity affected New Chitose Airport, which suffered damage to check-in counters and flooding in the passenger terminal building.

The airport operator said all flights to and from New Chitose Airport had been canceled for Sept. 6.

According to officials of various fire-fighting units, a large number of homes collapsed in the earthquake. Seventeen homes were reported damaged in Atsuma, three in Abira, two in Mukawa and one in Tomakomai.

Soil liquefaction also damaged roads, making many of them unpassable.

The quake also apparently sparked a fire at a steel plant in Muroran within the grounds of the Muroran Works of Nippon Steel & Sumitomo Metal Corp. However, the fire was nearly extinguished by 6:10 a.m. and no injuries or major damage were reported at the plant.