Lava and ash flows from Mayon volcano
A major eruption of a volatile Philippine volcano is still likely, and could be just weeks away, scientists have warned.
More than 30,000 people who live near Mount Mayon have now been moved to temporary shelters.
Government volcanologist Renato Solidum said lava flows and at least five small ash explosions had been seen recently.
He said the pattern was similar to Mayon's last eruption in 2006, when it expelled lava and steam for two months.
Philippine officials first raised the alert level for Mayon on Monday, but the volcano still shows signs that it might soon erupt.
Mr Solidum said that five new ash explosions, one of them reaching 550 yards (500m) in the air, had recently shaken the slopes of the volcano.
Another volcanologist, July Sabit, said he had noticed the formation of two lava domes at the crater during an aerial survey on Wednesday.
"This indicates pressure is building up from the inside, and the rising magma had accumulated at the mouth," he told the French news agency AFP.
But Mr Sabit added that scientists had not seen "intensified lava fountainings, or big earthquakes", which are often viewed as signs there could be a sudden massive explosion.
About 30,000 of the 50,000 people living in the vicinity of Mahon have now been evacuated and officials say they might have to spend up to four months in temporary shelters.
The Philippines is in the so-called Ring of Fire, an arc of fault lines circling the Pacific Basin that is prone to frequent earthquakes and volcanic eruptions.
Mayon, 330km (206 miles) south-east of the capital Manila, has erupted 48 times since records began.
The most violent eruption, in 1814, killed more than 1,200 people and devastated several towns.
However the volcano remains a popular tourist attraction and is famous for its perfect cone.