Temperatures inside the crater of the Nevado del Ruiz volcano in western Colombia continue to rise, as does seismic activity, a sign of a “very unstable” volcano and a possible imminent eruption, Colombian authorities warned today.

Nevado del Ruiz remains in the memory of everyone in Colombia for the tragedy of Armero, the second deadliest volcanic eruption of the 20th century, where almost 25,000 people died in November 1985 in a layer of mud and ash caused by the eruption.

And the martyrdom of Omaira Sanchez, 13 years old, who died in a hole of water where her legs were trapped, after three days of agony in front of the cameras, which had shocked the whole world.

The “orange” alert status at the volcano has remained since March 31, when the daily average of seismic tremors inside the volcano increased from 50 to 12,000. The “red” alert issued by the authorities may indicate an imminent eruption and immediate evacuation of the population on a large scale.

“Temperatures inside the crater rose significantly, exceeding 700 degrees Celsius,” Luis Fernando Velasco, the presidential adviser responsible for the matter, told local media.

In a latest volcano monitoring bulletin today, the Colombian Geological Survey warns again: “All indicators confirm that the activity of the Nevado del Ruiz volcano continues to be very unstable.”

The volcano has had several small eruptions over the past 10 years, but the geological service estimates that “a major volcanic eruption is likely in a few days or weeks.”

The latest photos released by authorities show the top of the mountain lit up by glowing materials overnight Thursday into Friday.

“Yesterday we saw a small eruption, a combination of very hot ash and magma trying to come out of the crater,” Velasco explained.

Nearly 57,000 people living in the 22 towns closest to the volcano are slowly being displaced from their homes, with farmers reluctant to abandon their crops and livestock.

On the central cordigera (mountain range) and the so-called Pacific Ring of Fire, Nevado del Ruiz is one of Colombia’s 25 active volcanoes.