Some thought it was a chemical attack or paranormal phenomena. However, scientists concluded that the lake experienced a release of carbon dioxide (CO2) from underwater sources. In bodies of water located in an area of volcanic activity, large amounts of gases, including carbon dioxide, can accumulate underground. When these gases come to the surface, they form a dense cloud that covers everything around them and kills living things.
The lake was previously calm, so no one expected that something like this could happen on it. Such emissions are quite rare, once in centuries, but they can be very dangerous. Similar phenomena have been recorded in different parts of the world, including Italy, Cameroon, Nigeria, Tanzania and Iceland.