After a small plane crashed close to the crater, rescuers from the Philippines are searching the volcano's slopes for survivors.
On Tuesday, the third day of the search on the Mayon volcano began with the deployment of helicopters, mountaineers, and sniffer dogs to the debris.
Two Australian consultants and two Filipino crew members of a geothermal company are among the missing.
The search has slowed since the plane was discovered on Sunday due to bad weather.
The risks near Mayon, which most recently erupted in 2018, have been signaled by local authorities. A permanent landslide and rockslide danger zone has been established within a 4km (2.5 miles) radius of the area.
Mudslides and flash floods have previously been caused by heavy rains washing down volcanic debris. The most recent incident occurred in 2020 when Super Typhoon Goni, locally referred to as Rolly, pounded the Philippine Pacific Coast.
The search's coordinator, Cedric Daep, told the regional governor's radio station, DZGB, that he hoped to find survivors by Tuesday.
On Saturday, the Cessna 340 aircraft vanished shortly after taking off for Manila from a nearby airport some distance from Mayon.
Authorities reported that the plane had been spotted 300 to 350 meters away from the crater.
Mayon was under the second-lowest of a five-step eruption warning system as of Tuesday. This indicates that a few gas emissions and rockfalls have been seen.
The Philippines experienced the disappearance of a Cessna aircraft for the second time in as many months. The first disappeared from view on January 24 and was unaccounted for.
In the nation of the archipelago, Cessnas are frequently used for pilot training and inter-island flights.