Mount Kelud in East Java, Indonesia, started eruption at 22:50 p.m. Jakarta time on Thursday, forcing thousands of residence living within 10 kilometers from the crater to evacuate, Umar Rosadi, a volcanologist at the national volcanology agency, told Xinhua by phone. "The rains of gravel and sand have reached 15 kilometers from the crater, hitting and impairing those being evacuated. This means that the evacuees must go farther than 15 kilometers," he said. Based on data recorded days before the eruption, the official said that there are at least 21,000 people living in the dangerous zone. The volcanology agency elevated the alert status of Mount Kelud to the top level at 21:15, according to Rosadi. The last volcanic eruption of Mount Kelud occurred in 2007 and its strongest eruption took place in 1919 and claimed 55 lives. Indonesia has just endured months long volcanic eruption of Mount Sinabung in North Sumatra that killed 17 people. Mount Kelud is among 129 active volcanoes in Indonesia, which is prone to seismic upheaval as it lies on the Pacific "Ring of Fire," an arc of volcano and fault lines surrounding the Pacific Basin.