TOKYO (Reuters) - Aftershocks rattled survivors of deadly Japanese earthquakes on Wednesday, nearly a week after the first one struck, as the area braced for heavy rain and the possibility of more landslides.

Rescuers using backhoes and shovels to dig through crumpled houses swept away in a landslide found a woman’s body, one of several people still missing. Another death was confirmed later in the day, taking the toll to 48.

Hundreds of people in the Kumamoto area of southwestern Japan spent another night in their cars, afraid to return to damaged houses.

Medical experts warned of the danger of potentially fatal blood clots from sitting too long in cramped conditions after a 51-year-old woman died and at least 12 people were hospitalized.

Eleven people appear to have died of illnesses related to their prolonged stay in evacuation centers, NHK national television said. The first quake hit late last Thursday and the largest, at magnitude 7.3, some 27 hours later.

“I keep thinking the earthquakes will stop, but they just go on and on,” one woman at an evacuation center in Mashiki, one of the worst-hit areas, told NHK.

“It’s really scary.”

Slideshow ( 4 images )

Of more than 680 aftershocks hitting Kyushu island since April 14, more than 89 have registered at magnitude 4 or more on Japan’s intensity scale, strong enough to shake buildings.

An earthquake of 5.8 magnitude struck off Japan’s northeast coast on Wednesday evening, the U.S. Geological Survey said, but there was no tsunami warning, nor were there any reports of damage or casualties.

The agency gave an initial magnitude of 6.1 for the quake that was centered 104 km (about 60 miles) southeast of Sendai, Honshu, near where a devastating quake and tsunami struck in March 2011, killing about 20,000 people.

On Kyushu, nearly 100,000 people were in evacuation centers, some huddling in blankets outside as night temperatures fell as low as 8 Celsius (46 Fahrenheit).

Heavy rain is expected over the area, raising fear that slopes weakened by the quakes could collapse.

Authorities have begun condemning buildings and other structures deemed unsafe. Hundreds, possibly thousands, of buildings collapsed, many brought down by their heavy roofs of traditional tiles.

Though public buildings must abide by stringent safety standards, the law is lax for private homes.

“When a big earthquake hits, structures may sustain damage that’s impossible to fix if there’s another quake within days,” said Akira Wada, professor emeritus at Tokyo Institute of Technology.

Most of those who were killed had returned to their homes after the first quake.