Indonesia’s rumbling Mount Lewotobi Laki Laki erupted Monday, sending a column of volcanic materials as high as 18 kilometers (11 miles) into the sky, depositing ash on villages and leading to flight cancelations, AP reports.

The volcano has been at the highest alert level since last month and no casualties were immediately reported.

Indonesia’s Geology Agency recorded an avalanche of searing gas clouds mixed with rocks and lava traveling up to 5 kilometers (3 miles) down the volcano’s slopes. Observations from drones showed lava filling the crater, indicating deep movement of magma that set off volcanic earthquakes.

The column of hot clouds that rose into the sky was the volcano’s highest since the major eruption in November 2024 that killed nine people and injured dozens, said Muhammad Wafid, the Geology Agency chief. It also erupted in March.

The volcano monitoring agency had increased the alert status for Mount Lewotobi Laki Laki to the highest level after an eruption on June 18, and more than doubled an exclusion zone to a 7-kilometer (4.3-mile) radius since then as eruptions became more frequent.

The 1,584-meter (5,197-foot) mountain is a twin volcano with Mount Lewotobi Perempuan in the district of Flores Timur.

Monday’s eruption was one of Indonesia’s largest since 2010 when Mount Merapi, the country’s most volatile volcano, erupted on the densely populated island of Java. That eruption killed 353 people and forced over 350,000 people to evacuate affected areas.

Indonesia is an archipelago of more than 280 million people with frequent seismic activity. It has 120 active volcanoes and sits along the “Ring of Fire,” a horseshoe-shaped series of seismic fault lines encircling the Pacific Basin.