TOKYO (Reuters) – a Powerful earthquake shook Northern Japan early on Tuesday, briefly disrupting cooling functions at a nuclear power plant and generating a small tsunami that hit the same Fukushima region devastated by the 2011 earthquake, tsunami and nuclear disaster.

A 7.4 magnitude earthquake felt in Tokyo sent thousands of residents fleeing to higher ground as dawn tore along the northeast coast.

There were no reports of deaths or serious injuries hours after the quake at 5: 59 a.m. (2059 GMT Monday). It was centered off the coast of Fukushima Prefecture at a depth of about 10 kilometers (6 miles), the Japan meteorological Agency (JMA) said.

A wave up to 1.4 meters high was recorded in Sendai, about 70 km North of Fukushima, where small waves are hitting ports in other areas of the coast, broadcaster NHK reported.

Television footage showed ships moving out to sea from harbors as tsunami warnings screamed after warning waves of up to 3 meters (10 feet) were released.

“We saw the high waves, but nothing that came through the tidal barriers,” said one of the residents of the city of Iwaki in an interview with NTV television.

Aerial footage showed tsunami waves flowing through rivers in some areas and some fishing boats were capsized at Higashi-Matsushima port before the JMA lifted its warnings.

The U.S. geological survey measured Tuesday’s earthquake at a magnitude of 6.9, at never at least 7.3.

All Japanese nuclear power plants in the area were shut down after the March 2011 disaster that knocked out cooling systems at Tokyo Electric Power Co’s Fukushima Daiichi plant, causing reactors to melt and spew radiation into the air, soil and sea.

The cooling system for storing spent nuclear fuel at a reactor at the Fukushima Daini plant was initially shut down on Tuesday, said a spokesman for Tokyo Electric Power, known as Tepco, but was restarted soon after.

Only two reactors are operating in Japan, both in the southwest. Nuclear power plants need cooling systems running even when stopped to keep spent fuel cool.

Tohoku Electric Power Co said there was no damage at the onagawa nuclear power plant, while Kyodo news Agency reported that there were no violations at the Tokai Daini nuclear power plant in Ibaraki Prefecture.

The Japanese Minister on the elimination of consequences of natural disasters Jun Matsumoto told reporters that reports of serious injuries have been reported. One woman suffered cuts to her head from falling dishes, Kyodo reported, citing fire officials.

Earthquakes are common in Japan, one of the most seismically active areas in the world. Japan accounts for about 20 percent of earthquakes of magnitude 6 or greater in the world.

On March 11, 2011, the earthquake was magnitude 9, the strongest earthquake ever recorded in Japan. The powerful tsunami it spawned knocked out the Fukushima Daiichi plant, triggering the worst nuclear crisis since Chernobyl a quarter of a century ago.

The systems were updated after the 2011 disaster to spread warnings more quickly, said Tsunetaka Omin, head of disaster management In Iwaki, a city in Fukushima Prefecture.

Previously, there were difficult directions where to evacuate. “But now, we basically just tell people to head away from the sea, on as much land as possible,” Omin said.

Authorities are also currently sending tsunami warnings to every mobile phone in the area and broadcasting on local radio.

Staying at a traditional Japanese hotel on the coast in the city of Ofunato with a dozen international high school students on a study tour, teacher Kathy Krauth said the shaking started seconds after the earthquake alarm on her phone went off.

“I felt that lessons 3-11 were really taken to heart,” said Krauth, who teaches a class on the March 2011 disaster and its aftermath. “The feeling was, we just don’t know, but we’ll be as careful as we can.”

Nissan Motor Co said it will suspend operations at its Fukushima engine plant at least until the latest tsunami warning is lifted. A spokesman said there were no injuries or damage at the plant, which was badly damaged in the 2011 disaster.

Toyota Motor Corp said all of its plants in northeast Japan are operating as normal.

The famous Japanese Shinkansen trains were stopped on one section of the track, and some other railway lines were also stopped.

Japanese financial markets were slightly affected, with the Nikkei 225 index closing 0.3 percent and the yen steady against the U.S. dollar.

Additional reporting by Chris Gallagher, Jon Herskovitz, Osamu Tsukimori, Aaron Sheldrick and William Mallard; Writing by Lincoln Feast; Editing by Paul Tait

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