Authorities warned a violent eruption may occur in hours or days, characterized by more rumblings and pyroclastic flows — superheated gas and volcanic debris that race down the slopes at high speeds, vaporizing everything in their path. After Monday's explosion, officials raised Mayon's alert level to four on a scale of five, and the danger zone was expanded to 8 kilometers (5 miles) from the crater, requiring thousands more residents to be evacuated, including at least 12,000 who returned to their homes last week as Mayon's rumblings temporarily eased and then scrambled back to the emergency shelters this week. In a phone call with CNN Philippines, Bichara said there was zero visibility in the municipalities of Guinobatan and Camalig, as well as the city of Ligao in Albay.
The Philippine Institute of Volcanology and Seismology raises Mount Mayon's alert level to 4, its second highest volcano category which indicates a hazardous eruption is imminent. Mayon's activity, which began the afternoon of January 13, 2018, has displaced about 40,000 residents in Albay Province on Luzon island.