The eruption of a volcano on the Indonesian island of Bali for the second time in a week spurred Indonesian and international airlines to cancel scores of flights this weekend and issue a “red warning” on Sunday as a plume of ash and steam spewed more than 14,000 feet into the sky.

Jetstar, KLM, Qantas and Virgin Airlines all canceled flights to and from the island, which is popular with tourists, after Mount Agung erupted around 5:30 p.m. Saturday. Ngurah Rai International Airport, the island’s main airport, remained open on Saturday, with flights arriving and leaving, though some 2,350 passengers from 14 canceled flights were stranded there.

But on Sunday, ash covered roads, cars and buildings near the volcano in the northeast of the island, while a red glow of what appeared to be magma could be seen overnight in photographs by Antara, the state news agency.

“The activity of Mount Agung has entered the magmatic eruption phase,” Gede Suantika, an official at the volcanology and geological disaster mitigation agency, told Reuters. “It is still spewing ash at the moment, but we need to monitor and be cautious over the possibility of a strong, explosive eruption.”.

The airport canceled 45 flights on Sunday, including those by Cathay Pacific Airways, Jetstar, AirAsia and Garuda Indonesia, officials said. More than 5,500 passengers were affected.

Indonesia upgraded its Volcano Observatory Notice for Aviation to red, its highest warning, and said the top of the ash cloud could reach 19,654 feet or higher.

The authorities warned those who live around the 9,940-foot volcano to stay outside a four-mile radius.

Agung also erupted on Tuesday, sending ash to a height of about half that it reached Saturday.

Bali, famous for its surf, beaches and temples, attracted nearly five million visitors in 2016, but business has slumped in areas around the volcano since September, when Agung’s volcanic tremors began to increase.

More than 145,000 people were evacuated that month, when the volcano showed signs of its e first major eruption in more than 50 years. But major activity failed to materialize, and many of those living in the area returned home. About 25,000 people are still displaced.

Indonesia’s National Disaster Mitigation Authority said in a statement that it was still assessing the risk but that “Bali’s condition remains safe.”

More than 1,100 people died when Mount Agung last had a major eruption, in 1963. Indonesia has more than 120 active volcanoes within its borders.