I’ve found a few more details about the ongoing activity at Huila in Colombia, including a video report from the BBC. It seems that the eruption at Huila is a photocopy of what happened at Nevado del Ruiz in 1985 in its style: hot ash and gasses erupted from the crater melted ice/snow near the summit to create a lahar – a deadly mix of volcanic material and water that ends up like a surging flow of liquid concrete. The lahars travelled down the Rio Paez valley (see linked map – the landslide on the map is not volcanically related).
Beyond the unfortunate victims caught in the mudflows, many roads and bridges have been damaged in the area near Belacazar. However, the BBC video does mention that many people were, luckily, given sufficient warning to escape the lahars – about an hour according to the man in the video – and resident went uphill to escape the flows. The death toll might be much lower than it could have been, a testament to how far Colombia’s volcano mitigation has come since the 1985 disaster.