Chief state volcanologist Renato Solidum says Mayon's alert level remains the same but that if magma continues to rise below the glowing crater it could erupt within weeks.

The country's most active volcano last erupted in 2006. Typhoon-triggered mudslides later that year buried entire villages, killing more than 1,000 people.

Two explosions early Wednesday sent ash and rocks more than half a mile (a kilometer) into the air, reaching nearby Camalig town along Mayon's foothills.

Authorities say they are ready to evacuate villages once the alert level goes up.