Magnitudes 7.1 & 6.6 quakes jolt Japan

(CNN) -- Fires burned in northeastern Japan Monday evening after a powerful earthquake rattled the region, triggering several landslides that trapped four people in one city.

The 6.6 - 7.1 magnitude quake was centered about 100 miles (164 kilometers) northeast of Tokyo and about 30 miles (50 kilometers) southwest of the crippled Fukushima Daiichi nuclear plant, according to the U.S. Geological Survey.

It caused several landslides in the city of Iwaki, including one that buried three houses and trapped four people inside, police in Fukushima Prefecture said. Authorities were trying to rescue the four. Their condition was not immediately known, police said.

The earthquake did not cause a tsunami.

Workers at Fukushima Daiichi nuclear plant evacuated briefly but soon returned to resume their efforts to cool the troubled facility.

Prime Minister Naoto Kan delayed a scheduled news conference as a result of the earthquake, his office said. The government wants to handle the immediate emergency before holding a news conference, the office said.

The Tohoku Electric Power Company said 220,000 households and businesses in Fukushima were without power after Monday's quake, which came a month after a deadly magnitude-9 quake and tsunami devastated the island nation.