Just more than 24 hours after powerful earthquakes struck a large island in southwest Japan, an even stronger quake has hit the same area.

The Associated Press quotes a Japanese official as saying 19 people were killed, bringing the total for the two big quakes to 29.

On Thursday evening local time, magnitude 6.2 and 6.0 quakes shook the city of Kumamoto and the surrounding area. They were followed by more than 100 smaller temblors, according to NHK — including several registering 5.0 or stronger, the U.S. Geological Survey says. The series of quakes shattered buildings. Hundreds of others were injured.

Then at 1:24 a.m. on Saturday, a magnitude 7.0 quake hit nearly the same location, according to the USGS. It was quickly followed by aftershocks of magnitude 5.8 and 5.7. (Japan is 13 hours ahead of the U.S. East Coast.)

The latest earthquake isn't considered an aftershock; instead, the quakes yesterday were foreshocks of the 7.0 quake, NPR's Nell Greenfieldboyce explains. She tells our Newscast unit that according to the USGS, the new quake "is six times larger than the biggest one yesterday and released 16 times more energy."

The USGS also says the 7.0 earthquake, like those on Thursday, was shallow — which is unusual for the region and can increase the degree of shaking and damage.

"I wouldn't be surprised to see more damage — I wouldn't be surprised to see more casualties than yesterday," John Bellini, a geophysicist with the USGS, tells our Newscast unit.

Japan's Meteorological Agency issued a warning for a possible small tsunami, up to 1 meter in height, but has since lifted the warning.

NHK reports that crews have been working to rescue people trapped inside buildings. The broadcaster also reports landslides, damaged roads and a break in a water reservoir.

There are reports of further damage at the historic Kumamoto Castle, the wire service says; the castle was damaged in Thursday's quakes as well.

The Sendai nuclear plant is within the area affected by the quakes; Japan's Nuclear Regulation Authority says no abnormalities have been found at the plant, according to the AP. (Sendai is currently the only nuclear plant operating in Japan. After the 2011 earthquake and tsunami led to the Fukushima disaster, the country shut down all nuclear power plants to assess them for safety. Sendai was the first to reopen and is the only one currently operational.)

The 7.0 earthquake hit as Kumamoto prefecture was working on repairing damage from Thursday and bracing for bad weather. NHK reported that even before Saturday's massive quake, officials with the meteorological agency had been concerned about forecasts for heavy rain and strong winds this weekend.

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