(CNN) -- Philippine authorities on Sunday raised the alert status of the country's most active volcano to level 4 and established an extended danger zone around it, saying an eruption is imminent.
The status change at the Mayon volcano "means that a hazardous explosive eruption is possible within days," according to the Philippine Institute of Volcanology and Seismology.
Earlier Sunday, the institute said the central Philippine volcano continues "to exhibit a high level of activity," adding that 222 volcanic quakes and tremors have been recorded in recent days. One was "an explosion-type earthquake" that launched a cloud of ash about 1,640 feet (500 meters) into the air, according to an institute statement.
The institute recommended extending already-established danger zones of nearly five miles (8 kilometers) south of the summit and 4.3 miles (7 kilometers) north of the summit.
In addition, "areas just outside of this extended danger zone should prepare for evacuation in the event explosive eruptions intensify," the institute said.
More than 30,000 people fled their homes last week ahead of an expected eruption, and authorities were attempting to evacuate about 50,000 people living around the 8,077-foot volcano.
People in surrounding Albay province have flocked to town centers to catch a glimpse of glowing lava cascading down the slopes of Mayon since the mountain began oozing fiery lava and belching clouds of ash last week.
The volcano, about 310 (500 kilometers) south of the Philippine capital of Manila, has erupted 49 times since its first documented eruption in 1616.
The Philippines is situated in the so-called Ring of Fire, an arc of fault lines circling the Pacific Basin that is prone to frequent earthquakes and volcanic eruptions.
In 1814, Mayon had its most violent eruption, killing more than 1,200 people. Its last major eruption was in 1993. Since then, it has remained restless, emitting ash and spewing lava.
VOLCANO ALERT LEVELS
Level O: No alert
Level 1: Abnormal
Level 2: Increasing unrest
Level 3: Increased tendency toward eruption
Level 4: Hazardous eruption imminent
Level 5: Hazardous eruption