Indonesian authorities have halted all air traffic at Bali’s international airport after raising the Agung volcano alert back to the highest level, and ordering people within 10 kilometers of the crater to evacuate out of fear of a potential big eruption.

As many as 100,000 people should evacuate expanded danger zone around Bali volcano, the Indonesian disaster agency said on Monday. Mount Agung volcano on the resort island of Bali has erupted two times in less than a week, firing columns of ash thousands of meters into the air. The increase in the volcano activity and discharges into the atmosphere prompted the local authorities to close off Ngurah Rai International Airport and issue the highest alert warning.

The airport, which was closed Monday morning local time, will remain closed until at least 7am local time Tuesday. The cancellation of flights will affect around 50,000 passengers who use the airport each day to come and depart the resort island.

Just before the airport closure, the Indonesian National Board for Disaster Management (BNPB) raised the alert level to Level 4.

“Mount Agung eruption continues to increase. The rate of eruption of the Great Volcano now rises from the phreatic to magmatic phase,” BNPB said. “This indicates the potential for a larger eruption is imminent,” noting that occasional weak blasts can be heard 12 kilometers from the peak.

Waspadai banjir lahar hujan (lahar dingin) di sekitar Gunung Agung. Banjir lahar hujan sudah terjadi di beberapa tempat di lereng Gunung Agung. Jangan melakukan aktivitas di sekitar sungai. via @Sutopo_BNPB#ElshintaNewsAndTalkpic.twitter.com/upJWyRRIjp — Radio Elshinta (@RadioElshinta) November 27, 2017

READ MORE: Erupting Bali volcano spews huge column of ash, forcing airlines to re-route flights (VIDEOS)

The agency advised communities, climbers and tourists around Mount Agung to stay at least 10 kilometers away from the crater. “People within a radius of 8 km and 10 km are urged to immediately evacuate in an orderly and calm manner,” BNPB added.

READ MORE: Volcano erupts on Indonesian resort island amid mass evacuations (VIDEOS)

Authorities also warned people to stay away from cold lava flows, known as lahar. "Lahar floods have already occurred in several places on the slopes," disaster agency spokesman Sutopo Purwo Nugroho said on Twitter, posting a clip of this phenomenon.