MANILA, Philippines (AP) — One of the Philippines’ most active volcanoes is showing signs of heightened unrest and an eruption is possible within weeks, government scientists warned Tuesday.

The Philippine Institute of Volcanology and Seismology raised the alert level to “critical” for Mount Mayon in eastern Albay province late Monday after recording an escalation of unrest over a 15-hour period, including 39 incidents of hot rocks falling in the summit area and 32 low-frequency volcanic earthquakes.