A large column of smoke streamed from Chile's Calbuco volcano Friday, prompting new warnings that it could erupt again after unexpectedly roaring back to life and forcing thousands to evacuate. As thick plumes of pale gray smoke began to billow again from the volcano's crater, the National Geology and Mines Service issued new warnings that a third eruption could follow the spectacular bursts of ash and lava that sent southern Chile into panic late Wednesday and early Thursday. Authorities ordered the preventive evacuation of some 2,000 people from three more towns at risk of flooding from snow and ice melting high in the mountains due to the volcano's heat, bringing the total number of evacuees to around 6,500. Additionally, about 300 farmers were affected by the eruption and authorities on Saturday planned to evacuate about 4,000 sheep and cattle. The ash cloud meanwhile continued to drift, disrupting flights across a large swath of South America, including planes from Paris, Sydney and Dallas that were forced to either turn back or land elsewhere. In Buenos Aires, on the other side of the continent, American Airlines, United, Delta and Air France all cancelled flights to and from Europe and the United States. Chilean authorities have declared a state of emergency, sent in the army and evacuated a 20-kilometer (12-mile) radius around Calbuco, which is located in Los Lagos, a region popular with tourists for its beautiful mountain landscapes dotted with volcanoes and lakes with black-sand beaches. As some residents dug themselves out from beneath the thick layer of ash that blanketed the area, others who were evacuated from their homes gathered at the police barricade outside the town of La Ensenada, anxious to check on their houses and feed their pets. On the other side of the security perimeter, the evacuation area was turned into a scattering of ghost towns blanketed with ash up to one meter (three feet) thick, an AFP photographer said. In La Ensenada, a town of 1,500 people that was the first to be evacuated, workers used heavy trucks to plow the roads clear as a handful of residents ignored the evacuation order to shovel the ash and debris off their rooftops. The weight of the ash caused some roofs to collapse. Authorities said that if the current conditions held, residents would be allowed to return home for a few hours in the afternoon to retrieve some belongings, after fleeing with nothing but the clothes on their backs. - Concern over ash, floods - Ash particles spread over southern Uruguay and a broad belt across central Argentina, though the national weather service said they were at high altitude and did not impair visibility. Experts cautioned that a third eruption could still follow. "We're still in what is considered the crisis phase," said Rodrigo Alvarez, head of the National Geology and Mines Service. "It's very difficult to say how explosive future eruptions will be, but we expect more activity similar to what happened" Wednesday and Thursday, said Carlos Cardona, a volcano expert at the service. President Michelle Bachelet, who flew to the affected area Thursday, warned the situation remained "unpredictable." There have been no reports of injuries so far, but officials said the ash could be harmful for people, animals, crops and infrastructure. Authorities handed out protective masks in affected towns in both Chile and Argentina. - String of disasters - The first eruption, which lasted about 90 minutes, spewed a giant mushroom cloud of ash into the sky, which turned hues of pink and yellow as the sun set over the area. Seven hours later, the volcano shot red and orange bursts of lava into the sky, as bluish-white bolts of lightning sliced through the billowing ash cloud. Until minutes before the first blast, volcano monitoring systems had picked up nothing. The 2,000-meter (6,500-foot) volcano had last erupted in 1961 and showed light activity in 1972, said the National Geology and Mines Service. It is the second eruption in Chile since March 3, when the Villarrica volcano emitted a brief but fiery burst of ash and lava. Chile has about 90 active volcanoes. The long, thin country has been hit by a series of natural disasters in recent months, from flooding in its usually arid north, home to the world's driest desert, to wildfires in its drought-hit southern forests.