The Volcanology and Geological Hazards Mitigation Center (PVMBG) raised the warning level for aviation activity around Bali on Saturday evening because of an eruption on Mount Agung.

“We raised the status to red [the highest warning level] as volcanic ash clouds had reached an altitude of more than six kilometers above sea level,” said Kasbani, the head of PVMBG, on Sunday as quoted by Antara news agency.

According to the Volcanic Observatory Notice for Aviation (VONA) system, winds carried the ash in an eastern and southeastern direction. Kasbani added that the information provided by the system would help pilots and airlines adjust their routes because of the volcanic activity.

Despite the raised alert status, I Gusti Ngurah Rai International Airport in the provincial capital of Denpasar was still operating as normal, an airport official said.

On Saturday, four airlines decided to ground at least 16 of their flights because of the increasing activity of the volcano in the afternoon.

The twelve departures affected include from Bali to Sydney, Adelaide and Melbourne by Jetstar, to Brisbane by Virgin Airlines, and two to Sydney and one to Amsterdam by KLM.

Mount Agung, which has been experiencing increased activity since Tuesday, erupted for the second time on Saturday.

The eruption caused volcanic ash to fall on nearby villages, forcing residents to flee to the southern part of the island.