A strong earthquake with a preliminary magnitude of 7.6 triggered tsunami warnings in some areas of Japan's northern coast on Monday and led to evacuation notices as authorities investigated the extent of the damage and whether there had been any casualties.

The Japan Meteorological Agency said the earthquake occurred off Aomori prefecture on Japan's main island of Honshu after 11 p.m. m. local time, and which was followed by an aftershock of magnitude 5.6.

The meteorological agency issued a tsunami warning for the prefectures of Aomori, Iwate and Hokkaido, and issued a tsunami warning for the prefectures of Miyagi and Fukushima.

At a port in Iwate prefecture, on the island of Honshu, tsunami waves of more than 0.6 were detected meters.

Waves of more than 40 centimeters were observed in the port of Mutsu-Ogawara, in Aomori prefecture, and in Urakawa, in Hokkaido, Japan's northernmost main island. A tsunami less than 30 centimeters high was observed in the Hokkaido city of Erimo.

No damage to nuclear power plants has been detected so far, Kihara said.

The extent of damage in populated areas was not immediately clear, officials said. In the Honshu city of Hachinohe, fires and power outages broke out, prompting emergency calls, and a local school was opened for residents to use as an evacuation shelter, Kihara said.

About 800 homes in the island's Iwate prefecture were left without power, he said. Highway and rail services were disrupted.

NHK, Japan's public broadcaster, said staff at a hotel in Aomori had reported that several people had been injured.

Kenta Kobayashi, a journalist in Tomakomai, Hokkaido, said he felt strong shaking. “I couldn't stand without holding something,” she said.

Japanese Prime Minister Sanae Takaichi told reporters that authorities would give residents any necessary evacuation instructions. Tsunami warnings and warnings are regularly issued in Japan after earthquakes. Last month, the weather agency briefly issued a tsunami warning when a magnitude 6.7 earthquake struck off the coast of Honshu island.

In March 2011, a magnitude 8.9 earthquake and tsunami They devastated the northeastern coast of Japan and knocked out the cooling systems of three reactors at the Fukushima Daiichi nuclear power plant. More than 19,000 people died in the earthquake and tsunami.

Christine Hauser is a Times reporter who writes breaking news, features and explainers.

Hisako Ueno is a reporter and researcher for the Times in Tokyo and writes about politics, business, work, gender and Japanese culture.