Authorities were forced to cancel a number of flights in the Indonesian tourist island of Bali after a volcano threatened to erupt, spewing ash and smoke 13,123 feet up in the air. As a result, thousands of tourists were left stranded, AFP reported

Mount Agung sent plumes of grey smoke into the air on Sunday, the third day in a week. Indonesia’s volcanology centre put out a red alert, warning airlines of a possible eruption. While the international airport in Bali is still open, at least 28 departing or arriving flights were delayed and cancelled, said airport spokesperson Arie Ahsanurrohim.

At least 2,000 passengers have been affected, mostly tourists from Australia. By Sunday afternoon, Qantas, Virgin and Jetstar airlines announced that they were resuming flights between Australia and Bali, The Sydney Morning Herald reported.

But hours later, Virgin said it was cancelling its services for the day as a precautionary measure. Several domestic flights to the nearby island of Lombok were also cancelled. The decision to delay or divert flights was up to individual airlines, Ahsanurrohim told AFP.

Mount Agung last erupted in 1963, killing 1,600 people. It started spewing ash again in September. Authorities then raised the alert to the highest level, and 1,40,000 people living nearby had to evacuate. By the end of October, the volcano’s activity reduced, people returned to their homes and the alert was lowered to the second-highest level. On November 21, Mount Agung rumbled again, forcing 25,000 people to seek shelter.

The alert level is still at the second-highest level. “The tremors and quakes caused by the volcano’s activities are significantly less than in September,” said Kasbani, the head of Indonesia’s volcanology centre.

Mount Agung is one of the more than 120 active volcanoes along the length of Indonesia, which is on the Pacific Ring of Fire.