LEGAZPI, Philippines (AP) — More than 9,000 people have evacuated the area around the Philippines' most active volcano as lava flowed down its crater Monday in a gentle eruption that scientists warned could turn explosive. The Philippine Institute of Volcanology and Seismology increased the alert level for Mount Mayon late Sunday to three on a scale of five, indicating an increased tendency toward a hazardous eruption. Lava flowed at least half a kilometer (less than half a mile) down a gulley from the crater and on Monday morning, ash clouds appeared mid-slope, said Renato Solidum, head of the volcano institute.