A group of 50 police officers and rescue workers had been combing the area beneath Mt. Kusatsu Shirane on Wednesday morning, a day after the surprise eruption.
"But we stopped it as volcanic tremors were detected," a Japanese police official told AFP.
"We'll discuss with experts to see if we'll resume our operation," he said.
There had not been any reports of missing people after the deadly eruption on Tuesday, which sent rocks and ash tumbling down the snow-covered slope of the volcano towards a ski resort below.
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But police and rescue workers combed the area today in case anyone had been left behind.
A soldier from Japan's Self-Defense Forces was killed in the incident, and seven others were injured, along with four civilians.
"Two of the seven soldiers became seriously ill and underwent operations yesterday," a defence ministry official told AFP.
"Their conditions have stabilised. All of them are still in a hospital," he said.
Japan's Meteorological Agency warned Wednesday that further volcanic activity could be expected.
The agency is setting up additional monitoring cameras and seismometers around the volcano to better track its activity, a government spokesman said.
Tuesday's eruption of Mt. Kusatsu Shirane was its first since 1983, but Japan has scores of active volcanoes and sits on the so-called Pacific "Ring of Fire" where a large proportion of the world's quakes and volcanic eruptions are recorded.
There are currently 111 active volcanoes in Japan, according to agency officials.