Officials on Sunday said that the death toll following the eruption of the highest volcano on Indonesia’s most densely populated island of Java has risen to 13, with seven people still missing.

Mount Semeru in Lumajang district in East Java province spewed thick columns of ash more than 12,000 meters (40,000 feet) into the sky, and searing gas and lava flowed down its slopes after a sudden eruption Saturday triggered by heavy rains. Several villages were blanketed with falling ash.

A thunderstorm and days of rain, which eroded and finally collapsed the lava dome atop the 3,676-meter (12,060-foot) Semeru, triggered the eruption, said Eko Budi Lelono, who heads the geological survey center.

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He said flows of searing gas and lava traveled up to 800 meters (2,624 feet) to a nearby river at least twice on Saturday. People were advised to stay 5 kilometers (3.1 miles) from the crater’s mouth, the agency said.

“Thick columns of ash have turned several villages to darkness,” said Lumajang district head Thoriqul Haq. Several hundred people were moved to temporary shelters or left for other safe areas, he said, adding that a power blackout hampered the evacuation.

The debris and lava mixed with rainfall formed thick mud that destroyed the main bridge connecting Lumajang and the neighboring district of Malang, as well as a smaller bridge, Haq said.

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Despite an increase in activity since Wednesday, Semeru’s alert status had remained at the third highest of four levels since it began erupting last year, and Indonesia’s Volcanology Center for Geological Hazard Mitigation did not raise it this week, Lelono said.

National Disaster Mitigation Agency spokesperson Abdul Muhari said at least 13 villagers died from severe burns and 57 were hospitalized, including 16 in critical condition with burn injuries. He said rescuers were still searching for seven residents and sand miners along a river in Curah Kobokan village who were reported missing.

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Entire houses in the village were damaged by volcanic debris and more than 900 people fled to temporary government shelters, Muhari said.

Television reports showed people screaming and running under a huge ash cloud, their faces wet from rain mixed with volcanic dust. The last time Semeru erupted, in January, there were no casualties.