TOKYO, Jan. 25 (Xinhua) -- Rescue workers resumed operations Thursday to search for people who may still be stranded in the wake of a volcano erupting in eastern Japan on Tuesday, killing one and injuring 11, local officials said.
The search operation at the Kusatsu Kokusai Ski Resort in Gunma Prefecture was suspended Wednesday due to volcanic tremors.
According to the Japan Meteorological Agency (JMA) 639 volcanic earthquakes were observed on Tuesday and 23 on Wednesday along with 4 volcanic tremors.
No tremors were observed as of early evening on Thursday, the agency said.
Firefighters and police personnel had been searching for people that may still be engulfed in the snow after the volcano at the Moto-Shirane peak of Mount Kusatsu-Shirane erupted Tuesday, triggering an avalanche at the nearby Kusatsu Kokusai Ski Resort.
A 49-year-old Ground Self-Defense Force (GSDF) sergeant major on a ski training operation at the resort was killed by volcanic rocks being launched in the eruption and 11 others were injured in the event.
On Thursday rescue officials reported finding volcanic rocks of up to 60 cm in diameter on one of the ski resort's runs and official warnings are in place for flying volcanic rocks within a 2-km red zone from the craters.
The JMA has kept its alert level at 3 from a maximum of 5, warning of further possible eruptions.
Mt. Kusatsu-Shirane comprises Mt. Shirane, Ainomine and the Moto-Shirane peak.
Initially the JMA had focused its attention on the Mt. Shirane peak as erupting due to it being the most active of the three having last erupted in 1983.
But the weather agency subsequently found that the Moto-Shirane peak, located about 2 km south of Mt. Shirane, which has been dormant for 3,000 years and has no monitoring equipment on the mountain, was the location of the eruption.
There are 110 active volcanoes in Japan and the weather agency permanently monitors 47 of them.
In September 2014, 63 people were killed on Mt. Ontake, on the border between Nagano and Gifu prefectures, in the the worst volcanic disaster in Japan in nearly 90 years.