MANILA (Reuters) - The Philippines lowered the alert at its restive Mayon volcano by one notch on Saturday after noticing signs of decreased activity, and cut to 6 kilometers (4 miles) a no-go zone at the mountain.
Residents close to the no-go zone in the central province of Albay were warned of possible rockfalls, pyroclastic flows, ash emissions, and lahar (mud lava) in water channels, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said in its latest bulletin.
"The lowering of the alert level from four to three should not be interpreted that the unrest of the volcano has ceased," PHIVOLCS said in its bulletin, adding any possible sudden explosions were likely to occur only within the no-go zone.
On December 20, authorities raised the alert level to four and extended the no-go zone to 10 km at Mayon, known for its near-perfect cone shape, in the coconut-growing central Bicol region.
In the volcano's last major activity in 2006, lava oozed from it for two months.
There are no major industries around the volcano, with most farming activities in the area confined to subsistence crops.
Albay Governor Joey Salceda said he has allowed most residents to go home, but those coming from two villages near the volcano would have to stay at evacuation centres. At its peak, there were 50,000 people seeking shelter in public schools in the province.
On Saturday, PHIVOLCS said it detected 13 volcanic earthquakes and 68 rockfall events from Mayon, as well as weak white steam emission from the summit crater.
"The latest activity of Mayon still indicates that its overall state of unrest remains relatively high. However, this phase of ... moderate seismicity, high volcanic gas outputs and continuing glow of the summit (is) normally associated with very gradual return to the repose period," PHIVOLCS said in its bulletin.
Mayon is the most active of 22 volcanoes in the country, having erupted more than 50 times in the last four centuries. The most destructive eruption came in February 1841 when lava flows buried a town and killed 1,200 people.
The Philippines lies on the "Ring of Fire," a belt of volcanoes circling the Pacific Ocean that is also prone to earthquakes.
(Editing by Jerry Norton)