Japan issued a tsunami warning after a powerful 7.1-magnitude earthquake struck the southwestern island of Kyushu on Tuesday. The Japan Meteorological Agency said the quake hit at 4:27 p.m. local time and reached a maximum intensity of 7 on Japan’s Shindo seismic scale. About 45,000 households and facilities in the Kumamoto area lost electricity, according to local utility Kyushu Electric Power.

The meteorological agency said tsunami waves could reach up to one metre. Public broadcaster NHK reported that waves of that height may already have struck. About half an hour after the earthquake, an NHK local reporter said shaking was still continuing and was so strong in the newsroom that it was difficult to remain standing.

Japan’s Nuclear Regulation Authority said no immediate abnormalities had been detected at nuclear power plants. Kyushu Electric Power said three operating nuclear reactors in the region were functioning normally during the quake. The NHK reporter urged people to remain alert for possible further tremors after describing the initial shaking as too intense to stand through.