Phillippines ? The Philippines’ most active volcano could have a huge eruption within days, officials warned Sunday after detecting a drastic surge in earthquakes and eerie rumbling sounds in surrounding foothills. Tens of thousands of villagers have been evacuated as a precaution.

Scientists raised the alert level for the Mayon volcano after 453 volcanic earthquakes were detected in a five-hour span Sunday, compared to just over 200 Saturday, said Renato Solidum, chief of the Philippine Institute of Volcanology and Seismology.

The five-step warning system was raised to level four, meaning a hazardous eruption “is possible within days.” Level five is when a major eruption has begun.

Army troops and police will intensify patrols to enforce a round-the-clock ban on villagers moving within a five-mile danger zone around the 8,070-foot mountain, said Gov. Joey Salceda of Albay province, about 210 miles southeast of Manila.

More than 40,000 villagers have been moved to school buildings and other emergency shelters, but some have still been spotted checking on their farms in the prohibited zone. Salceda said about 5,000 more villagers were being moved from the volcano, most of them staying in and around Legazpi city, about nine miles away.

The cone-shaped volcano began emitting red-hot lava and puffing columns of ash last week. It belched a plume of grayish ash half a mile into the sky Sunday, and lava has flowed about 2.8 miles down the mountainside, Salceda said.

A major eruption can trigger pyroclastic flows — superheated gas and volcanic debris that can race down the slopes at very high speed, vaporizing everything in their path. There can be more extensive ejections of ash, which can drift toward nearby townships.