The Philippine Institute of Volcanology and Seismology said Monday in a statement an explosion-type earthquake launched a cloud of ash about 500 meters into the air.

Authorities raised the alert status to Level 4 on Sunday which means that a hazardous explosive eruption is possible within days, the country's national news agency reported Monday.

Officials said it was getting closer to a major eruption that could come at any time.

 Audible booming and rumbling sounds were first reported in the eastern flank of the volcano on Sunday afternoon and 1,942 volcanic earthquakes were detected by the institute's seismic network in the 24 hours to 7 a.m. local time on Monday, the institute said.

 More than 9,000 families are being housed in evacuation camps after authorities raised the alert status.

Mayon volcano last erupted in 2006, when about 30,000 people were moved. Another eruption in 1993 killed 79 people but the most destructive came in 1814, killing more than 1,200 people and burying a town in volcanic mud.

The volcano, located about 500 km (310 miles) south of the Philippine capital of Manila, has erupted 49 times since its first documented eruption in 1616.