LEGAZPI CITY, Philippines—Observations of residents living near Mayon Volcano have prompted the Philippine Institute of Volcanology and Seismology (Phivolcs) to closely monitor the volcano for possible danger signs.

“We have observed that the crater glow has become brighter and very much visible to the naked eye in the past few days compared to previous months,” said Emma Luminao, a resident of the village of Kilicao, in the town of Daraga, Albay.

But Phivolcs has yet to assess the condition of Mayon after conducting an aerial survey and monitoring the seismic activity around the volcano before raising or lowering the alert level, resident volcanologist Eduardo Laguerta told the Philippine Daily Inquirer in a phone interview.

Phivolcs maintains Alert Level 1 over Mayon Volcano and is reminding the seven-kilometer danger zone at the southeastern flank and the six-kilometer permanent danger zone in other areas remain off-limits.

Laguerta said Phivolcs has been closely monitoring the volcano.

“The increase in intensity of the crater glow and the daily volcanic quakes of up to 10 is the reason why we cannot remove the alert level,” Laguerta said.

But he said that if seismic activity and other signs, such as ground deformation, sulfur dioxide emission rate, intensify, the institute might heighten the alert level.

Mayon Volcano has been on Alert Level 1 since October 2006, after being lowered from Level 3 when it spewed lava in July 2006.