The Philippine Institute of Volcanology and Seismology, or Phivolcs, on Monday said no magma has risen in Mayon Volcano in Albay province despite a phreatic eruption on Sunday.

Phivolcs Director Teresito Bacolcol said in a television interview they have not monitored any further activities from Mayon up to Monday. “This is good. It means no magma is rising,” he said in Filipino.

Mayon’s phreatic eruption started at 4:37 p.m. on Sunday, lasting 4 minutes and 9 seconds. The volcano generated a booming sound, rockfalls, pyroclastic density currents, and a 1,200-meter-high plume that drifted to the southwest.

According to Phivolcs, phreatic, also called steam-driven, eruptions are sudden-onset and short-lived events that happen without warning or any precursors.

Bacolcol noted there are still hot materials from the last year’s eruption in the crater of Mayon “and when this comes into contact with water, it may release steam, ash and gases.”

Phivolcs recorded an effusive eruption from 11 June to 8 December last year.

Bacolcol cautioned the public to avoid venturing inside the six-kilometer permanent danger zone since phreatic eruptions could be sudden.

“It is not as violent as a magmatic eruption but it can still send ash and rocks in the air,” he said. But so far, no ashfall has been reported in the barangays near the volcano.

In its latest bulletin, Phivolcs said the crater glow in Mayon can be seen with the naked eye. It emits moderate voluminous plumes drifting northwest.

Since 8 December, Mayon’s alert category has stood at Level 2, which means decreased unrest.