Scientists in the Philippines renewed warnings of a major explosion at the Mount Mayon volcano, describing a sudden period of quiet as "ominous".
The volcano has been emitting ash and red-hot lava
A drop in gas emissions and earthquakes sparked fears that the crater had plugged itself, increasing the likelihood of an explosive eruption.
Around 40,000 people have been evacuated from Mayon's slopes and are living in makeshift camps.
The volcano in Albay province began emitting lava on 14 July.
Fears that the full moon's gravitational pull could trigger an eruption on Wednesday were not realised, but as lava continued to flow, experts warned of "unusual quiet".
The number of earthquakes at the volcano dropped from 21 on Wednesday to three on Thursday and sulphur dioxide emissions were also down, Ernesto Corpus of the Philippine Institute of Volcanology and Seismology said.
"It is at this time that the volcanic activity could be gearing up for a bigger explosion," he told the French news agency AFP. "This kind of unusual quiet is ominous."
Thousands of residents have been moved from villages within an 8km (5 mile) danger zone around the volcano and are taking shelter in temporary camps.
Troops are patrolling the danger zone to make sure everyone has been evacuated.
Some farmers had been reluctant to leave their land, but soldiers said fewer people were trying to return since the lava had come closer.
"They are more afraid now," one soldier told AFP.
Military officials said they were seeking a temporary truce with local communist guerrillas after an attack on Tuesday on a barracks in the provincial capital, Albay, left five soldiers injured.
Albay Governor Fernando Gonzalez called for a truce with the New People's Army while the military was working on the evacuation.
"All of us want an end to this conflict but more so in this period when everybody is busy with this emergency," he said.
Mayon is the most active volcano in the Philippines, having erupted about 50 times in the past 400 years.
Its most violent eruption, in 1814, killed more than 1,200 people. Another 75 people died during an eruption in 1993.