MEDAN, Indonesia (AP) — A rumbling volcano in western Indonesia on Sunday unleashed an avalanche of scorching clouds down its slopes.

Authorities are closely monitoring Mount Sinabung on Sumatra, one of Indonesia’s main islands, after sensors picked up increasing activity in past weeks.

The volcano in North Sumatra province was shooting smoke and ash more than 1,000 meters (3,280 feet) into the air on Sunday morning, and hot ash clouds traveled 1 kilometer (0.6 mile) southeast, Indonesia’s Volcanology and Geological Hazard Mitigation Center said.

Villagers were advised to stay 5 kilometers (3.1 miles) from the crater’s mouth and should be aware of the peril of lava, the agency said. Air travel was not impacted by the ash so far, the Transport Ministry said.

There were no casualties from the eruption, said Armen Putra, an official at the Sinabung monitoring post. He said villages outside the red zone were not in immediate danger.

Some 30,000 people have been forced to leave homes around Sinabung in the past few years.

The 2,600-metre (8,530-feet) Sinabung was dormant for four centuries before exploding in 2010, killing two people. Another eruption in 2014 killed 17 people, while seven died in a 2016 eruption.

The volcano, one of two currently erupting in Indonesia, has sporadically come to life since then.

Sinabung is among more than 120 active volcanoes in Indonesia, which is prone to seismic upheaval due to its location on the Pacific “Ring of Fire,” an arc of volcanoes and fault lines encircling the Pacific Basin.