Lumajang, East Java. Mount Semeru erupted on Monday morning, sending thick ash plumes and volcanic debris into the air and prompting authorities to raise the alert status to Level III.

Residents living on the slopes of the volcano in Lumajang Regency have been urged to remain outside an 8-kilometer radius from the summit, as authorities warned of the risk of deadly pyroclastic flows and lava if the exclusion zone is ignored.

Indonesia’s Center for Volcanology and Geological Hazard Mitigation (PVMBG) said the eruption sent volcanic material up to about 1,100 meters above the peak. Based on PVMBG data, the eruption occurred at 6:51 a.m. local time (23:51 GMT Sunday).

“The ash column was observed to be white to gray in color, with moderate intensity drifting southward. At the time this report was issued, the eruption was still ongoing,” said Liswanto, an officer at the Semeru Observation Post.

There have been no immediate reports of significant damage or casualties. However, authorities also advised residents to avoid river channels that could carry cold lava flows, particularly during rainfall.

Mount Semeru, locally known as Mahameru or “The Great Mountain,” is one of Indonesia’s most active volcanoes and poses persistent risks to nearby communities. A major eruption in 2021 killed at least 22 people and injured dozens, as lava and ash buried several villages. Heavy rains at the time also triggered destructive lahar flows, inundating homes and vehicles.

Semeru is part of the Pacific Ring of Fire, a zone of intense seismic activity that hosts more than 130 active volcanoes across Indonesia, underscoring the country’s ongoing exposure to volcanic hazards.