Thousands of travellers were left stranded Tuesday on the resort island of Bali as the eruption of the Mount Agung volcano forced the closing of the island’s international airport for another day.

Continuing tremors radiated from the volcano, an indication of potentially increasing danger, Indonesian officials and volcano experts said.

“Magma has been at the surface for a few days now,” Janine Krippner, a Pittsburgh-based volcanologist, said by email. “The risk now is the possibility of a larger eruption.”

Ngurah Rai International Airport in Denpasar, Bali’s capital, was scheduled to remain closed until Wednesday morning. But the continuing eruption could further delay the opening of the airport, where flights have been grounded since Sunday.

The international airport on Lombok, an island neighboring Bali, was also closed Monday night but reopened Tuesday, according to AirNav Indonesia, a state-owned air navigation company.

On Monday, the government raised the volcano alert to the highest level and expanded an evacuation zone around Mount Agung to a 6-mile radius.

Sutopo Purwo Nugroho, a spokesman for Indonesia’s national disaster management agency, said Tuesday that more than 29,000 people had moved to established camps. An unknown number have relocated elsewhere, he said in a written statement. Others remained at home for various reasons, including to watch over homes and livestock, Sutopo said.

Officials say 90,000 to 100,000 people live in villages within the danger zone alongside the mountain, and as many as 150,000 may need to relocate. In September, when the volcano threatened to erupt, 145,000 people evacuated but later returned home.

Columns of ash continued to rise more than 2 miles above the crater, with the glowing red of lava visible at night. The volcano is emitting constant tremors, Sutopo said Tuesday afternoon on Twitter.

Two distinct columns of ash billowed from the volcano, one light grey and the other a darker shade. Experts said that was an indication that two vents had opened: one emitting more steam and the other spewing more ash from magma.

Indonesia’s Ministry of Energy and Mineral Resources said data from a NASA monitoring satellite showed a thermal anomaly in Mount Agung’s crater, indicating a significant amount of magma near the surface.

More than 400 flights were cancelled Tuesday, with about 60,000 passengers affected, Indonesia’s Ministry of Tourism said.

Bali’s governor has ordered hotels to provide a night of free accommodation for tourists stranded by canceled flights. Tourism officials have advised visitors to travel by bus and ferry to Surabaya, a major city in East Java, to fly on to other destinations.

Emilio Kuzma-Floyd, an Australian photographer who lives in Canggu, on Bali’s southwestern coast about 40 miles from Mount Agong, said he noticed the first ash from the volcano fall near his home Tuesday morning.

“All of a sudden there’s more sense of urgency,” he said, “a lot more people talking about leaving, talking about going far west into Java and leaving from there.”