About 100,000 people near Bali's Mount Agung have been ordered to evacuate as officials fear a major eruption. <br/><br/>Indonesian authorities have raised the state of alert to its highest level and expanded the exclusion zone around the rumbling volcano. <br/><br/>The island's airport has now closed, leaving thousands stranded in the tourist hotspot. Authorities say dark smoke and ash have been billowing up to 11,150 ft above the mountain's summit. <br/><br/>Officials have warned residents to stay away from rock and debris flows known as lahars, which have been spotted flowing down from the mountain. <br/><br/>Mount Agung's volcanic tremors first began in September. <br/><br/>The National Board for Disaster Management raised the alert to level four because of the possibility and imminent risk of disaster. <br/><br/>Geologist Mark Tingay of the University of Adelaide said that Mount Agung now appears to be entering the next phase with a magmatic eruption, where the glow of lava is visible from the crater.