BALI, Indonesia — Following massive plumes of smoke and volcanic eruptions over the weekend, Indonesian authorities raised their alert for the Mount Agung volcano here to the highest level possible on Monday. Indonesia's National Board for Disaster Management said that the "potential for a larger eruption is imminent." Authorities closed Bali Ngurah Rai International Airport, projecting it will reopen Tuesday at 7 a.m. local time, as the volcano spewed ash into the sky. Thousands of passengers were stranded as flights by Jetstar, Qantas, Virgin, KLM and Singapore Airlines were among those grounded.

A sign in Bali warns of lava and danger. CNBC's Uptin Saiidi

Sandra Santana, a client relationship manager who lives in Singapore, was planning to depart Sunday night from Bali to Singapore after a holiday get a way. She found out her KLM flight was canceled due to volcano activity upon arriving to the airport Sunday night. "I didn't know about the volcano. If I knew I wouldn't have come to Bali and I will try to postpone my trip," she told CNBC. KLM arranged for passengers to be put in a beach hotel near the airport. Santana spent the night there and was told she would be rebooked on another flight on Monday. Upon waking up on Monday morning, though, Santana found out that all flights in and out of Bali were canceled. "I am not stressed yet, but I will be if the airport is shut down tomorrow again," she said. She is now considering riding a ferry over to the island of Java and taking an 11-hour drive to the city of Surabaya with hopes of catching a flight from the airport there.

A man and son in Bali look out for the volcano covered by smoke and fog at Geological Agency of the Ministry of Energy and Mineral Resources CNBC's Uptin Saiidi