The Philippine Institute of Volcanology and Seismology (Phivolcs) has raised the alert status of Kanlaon volcano to level 1 or "from normal to abnormal," according to the Office of Civil Defense (OCD) in Negros provinces. The OCD explained that an alert level 1 status meant that the volcano, which straddles the provinces of Negros Occidental and Negros Oriental, had entered a period of unrest. The local government units and the public are strictly reminded that entry into the four-kilometer radius Permanent Danger Zone (PDZ) is strictly prohibited due to the possibilities of sudden and hazardous steam-driven or phreatic eruptions, Phivolcs said. Civil aviation authorities must also advise pilots to avoid flying close to the volcano's summit as steam and other volcanic debris from a possible sudden phreatic eruption could be hazardous to aircraft. The Phivolcs had monitored an increased seismic activity that could be succeeded by steam-driven phreatic eruptions at the summit crater, despite the absence of visible degassing or steaming from the active vent this year, the OCD said in a statement. Kanlaon volcano's seismic monitoring network had recorded a total of 244 volcanic earthquakes since June 24. Ground deformation data from continuous GPS measurements indicated that the Kanlaon edifice remains inflated since December 2015, it added. "These parameters indicate that volcanic processes are underway deep beneath the edifice that may be caused by deep-seated degassing or hydrothermal activity or magmatic intrusion," Phivolcs said.