MANILA (UPDATE 2) - Five people including 4 foreigners were killed by falling rocks after Mayon Volcano spewed ash Tuesday morning, a National Disaster Risk Reduction and Management Council (NDRRMC) official said.
NDRRMC executive director Eduardo del Rosario said the 5 fatalities were among the at least 20 mountaineers who went up the volcano in three groups.
Seven hikers were injured. Del Rosario said a chopper was already on its way to rescue trapped mountaineers. said the 5 fatalities were part of a group of climbers that included 5 foreigners and 3 Filipino tour guides. In that group, 4 foreigners of unknown nationalities and a local tour guide, identified only as "Jerome", were killed after being hit by falling rocks.
He said another group of 7 climbers took the Santo Domingo route up the volcano and were also hit by falling rocks.
He said 3 of the Mayon climbers of the Santo Domingo group were injured. Volcano tour guide Kenneth Jesalva, who went up the Malilipot route with the first group, said they first heard a loud rumbling before they were hit by volcanic rocks.
"Paakyat kami noon sa taas, nagpapahinga kami saglit at may narinig na kaming malakas na gulong ng mga bato. Iyung iba po naming kasamahan natamaan ng bato," Jesalva told ANC.
"Tumakbo po kami sa may safe na lugar, yung bato na mag-cocover sa amin, pero di talaga kinaya," he added. The bodies have yet to be brought down to the base camp, Jesalva said.
Philippine Institute of Volcanology and Seismology (Phivolcs) executive director Renato Solidum explained that the spewing of ash was caused by a hydro-thermal explosion. This type of explosion is also called "phreatic".
Solidum explained that a hydro-thermal explosion is stream-driven, which means that the volcano has let out steam that got trapped over time.
"The steam column that was produced was grayish, but mainly it is water. There is not much pressure on it. There is no new magma yet… The steam carried with it the old ash at the crater of the volcano." Solidum told ANC.
"It is a normal process in any volcano. If you look at Mayon Volcano, it continuously moves steam, even other volcanoes in the country. But once that steam is trapped, there can be pressure and that can trigger a shallow explosion," Solidum added.
Phivolcs said the wind was forcing the ash to go west, towards Albay's 3rd district, consisting of Guinobatan, Jovellar, Libon, Oas, Polangui, and Pio Duran.
Solidum said there is no way to predict if another ash explosion will occur.
"In previous episodes of eruption of Mayon Volcano, sometimes other ash explosions would happen, but the interval would not be very regular," Solidum said.
"We don't know when that will happen. We always reiterate that people should be careful especially those in the permanent danger zone. We have sufficient instrumentation there - cameras, seismic instruments. What we need to do is to evaluate the condition of the volcano continuously."
Solidum said Phivolcs is maintaining alert level 0 for Mayon, since there is no new magmatic activity yet.
In its latest advisory, Phivolcs said a volcanic eruption is not imminent.
Governor Salceda, meanwhile, said all "human activities" within the 6-kilometer radius permanent danger zone of the volcano have been suspended.
The permanent danger zone covers some parts of Legazpi, Santo Domingo, Malilipot, Bacacay, Tabaco City, Ligao, Guinobatan, Camalig and Daraga.