Mayon volcano began erupting ash on January 13 and has since erupted ash and lava. Photos: The Philippine Institute of Volcanology and Seismology

Rescue workers have evacuated more than 70,000 people from around the erupting Mayon volcano in the northeastern Philippines, but scientists have warned that magma is still building up under the ground and gas and lava emissions could continue for several months.

Mount Mayon remained at an alert level of four on a scale of five yesterday, which indicates another eruption could occur at any time. The alert level was first raised to four on Monday, after scientists from the Philippine Institute of Volcanology and Seismology said there had been a series of superheated lava flows down the slopes.

Lava fountains that were 500 to 600 meters high erupted on Tuesday evening, lasting for more than an hour,  ABC News reported. There were additional flows on Wednesday and early yesterday.

Worryingly, there were signs that the volcano’s cone was still swelling underneath from a build-up of magma, creating more pressure on the surface that will eventually have to be relieved through an eruption.

Ash and lethal sulfur dioxide gases began trickling out of Mayon, the Philippines’ most active volcano, at irregular intervals on January 13. Three days later a state of emergency was declared in the surrounding province of Albay on the island of Luzon, CNN Philippines reported.

The volcano has erupted about 50 times in the past 500 years, with the most destructive occurring in 1814 when 1,200 people were killed and the town of Cagsawa was buried.

There have been no reports of deaths or injuries from the current eruption, but there are concerns for the welfare of the 74,000 people evacuated from the eight-kilometer exclusion zone around the crater. They are being housed in temporary shelters at a safe distance.