Niigata Prefecture authorities sought Wednesday to prevent natural dams formed by landslides set off by recent strong earthquakes from bursting and thus causing secondary disasters.

Meanwhile, the death toll from the temblors rose to 38 as authorities counted the Oct. 24 death of a 67-year-old company executive as quake-induced.

According to prefectural police, Akira Yano, of the city of Uonuma, died of heart failure believed caused by stress and fatigue following the quakes.