Indonesian rescuers are searching for 12 people apparently still missing after a furious eruption of the Mount Marapi volcano killed at least 11 climbers.

Marapi spewed thick columns of ash as high as 3,000 metres (9,840 feet) in Sunday’s eruption, and hot ash clouds spread over several kilometres. Nearby villages and towns were blanketed by tonnes of volcanic debris.

West Sumatra’s Search and Rescue Agency head Abdul Malik said rescuers found 11 bodies of climbers as they searched for those still missing and rescued three others on Monday morning.

Marapi has stayed at the third highest of four alert levels since 2011, a level indicating above-normal volcanic activity and prohibiting climbers or villagers within 3km (1.8 miles) of the peak, said Hendra Gunawan, the head of the Center for Volcanology and Geological Disaster Mitigation.

About 75 climbers had started their way up the nearly 2,900-metre (9,480-foot) mountain on Saturday and became stranded. Eight of those rescued on Sunday were rushed to hospitals with burns and one also had a broken limb, said Hari Agustian, an official at the local Search and Rescue Agency in Padang, the West Sumatra provincial capital.

All of the climbers had registered at two command posts or online through West Sumatra’s conservation agency before they climbed, Agustian said. It was possible others took illegal roads or local residents were active in the area, but it could not be confirmed, he said.