More than 170 climbers, porters, guides, and tourism officials stranded on Mount Semeru in East Java have been reported safe following a sudden volcanic eruption, Indonesian authorities said on Thursday.

“They are safe and now being helped to return,” said Priatin Hadi Wijaya, head of the Centre for Volcanology and Geological Disaster Mitigation (PVMBG), during a video news conference.

Stranded Climbers Rescued

At least 178 people were caught on the 3,676-metre (12,060-foot) peak in Lumajang district on Wednesday, primarily at the Ranu Kumbolo camping area, which is located 8km (5 miles) from the crater and outside the main danger zone.

Another official, Hetty Triastuty, confirmed that the campsite on the northern slope of Semeru was not in the path of the pyroclastic flow, though climbers may have been exposed to volcanic ash.

Volcanic Activity and Alert Status

Mount Semeru erupted on Wednesday afternoon, sending ash and gas over 13km (8 miles) into the air, prompting authorities to raise the alert to the highest level. Semeru, also known as Mahameru, is the tallest peak in Java and sits on the Pacific “Ring of Fire”, a region prone to volcanic eruptions and earthquakes.

Aerial photos captured the pyroclastic flow moving south-southeast from the crater, highlighting the potential danger to surrounding areas.

Local Impact and Damage

Nearly 900 people took refuge in shelters established in schools, mosques, and village halls, according to Sultan Syafaat from Indonesia’s disaster management agency.

Residents described the eruption as terrifying. Faiz Ramadhani, a local, said:

“At four o’clock in the afternoon, it was like midnight. It was very dark.”

Some homes near the volcano were partially buried by volcanic ash and rock fragments. Nurul Yakin Pribadi, head of Supiturang village, reported that a metre-high layer of volcanic material damaged his house and several others in the village.

Historical Context and Volcanic Risk

Mount Semeru has erupted numerous times over the past 200 years, including a deadly eruption in 2021 that killed 62 people and buried villages in hot ash. Indonesia is home to nearly 130 active volcanoes, the most of any country, making monitoring and disaster preparedness critical for communities, transport routes, and aviation.

Authorities continue to monitor Semeru’s activity closely, prioritizing evacuation, rescue operations, and public safety for residents and visitors in East Java.