A reconnaissance flight revealed an absence of steam and gas escaping from a mountain that normally vents such clouds every day.
Scientists say that, combined with a new distinct pattern of tremors, indicates energy is building up inside the volcano in the form of trapped gases.
The Southern Andean Vulcanology Observatory says it has registered as many as 60 to 70 seismic events per day, and has issued a “yellow alert.”
That means tourists and other members of the public are prohibited from venturing to within a 2.5-mile radius around the crater.
Local businesses told El Mercurio that such a ban causes a significant loss in tourist revenue.
An eruption of Llaima on New Year’s Day 2008 prompted hundreds of people to evacuate their homes as ash from the blast traveled as far away as Argentina. More powerful eruptions occurred in 1927, 1957 and 1994.
Photo: Flickr - urbatem2 (Creative Commons)