LEGAZPI CITY -- The Philippine Institute of Volcanology and Seismology in Manila sent a two-man team to Albay province Friday to measure the swelling of Mayon Volcano's slopes following observations of increased abnormal activity succeeded by a mild ash explosion Sunday, an official said here.

Alex Baloloy, senior science research analyst at the Phivolcs Mayon Observatory in Daraga, Albay, said the engineering team would monitor changes in the volcano's ground deformation.

He said Mt. Mayon's volcanic edifice has been showing swelling by up to 12 millimeters since May, which indicated magma movement inside.

"The team is here to monitor changes in ground deformation, which is a key parameter in explaining the volcano's ongoing abnormal behavior," Baloloy said in a mobile phone interview.

Baloloy added that there were not much significant changes after the Sunday explosion except for an increase in the number of volcanic earthquakes daily.

Latest bulletin from Phivolcs-Manila showed that there were 11 volcanic earthquakes over the past 24 hours with moderate steam emission from the summit and crater glow at night.

After Mt. Mayon, the team will also monitor Mt. Bulusan, another active volcano in Sorsogon province.

Albay Governor Joey Salceda has ordered a stop to all human tourism and farming activities within the six-kilometer-radius permanent danger zone.

Mt. Mayon is an attraction to mountain climbers and orchid collectors.

The public is advised to keep off active river channels and lahar zones.

In the southeast quadrant where the crater rim is lowest, the danger zone had been extended to 7 kilometers following the Typhoon “Reming” lahar tragedy which killed almost a thousand in 2006.

Alert Level No. 1 remains hoisted over the 2,463-meter volcano, which is vying for a spot in the Seven Wonders of Nature online search.