MANIZALES, COLOMBIA (CBS) -- A rising smoke plume from a Colombian volcano put nearby cities and towns on alert as it continued to emit smoke, vapor and ash Monday.
The Nevado del Ruiz volcano, located in central Colombia about 130 kilometers (80 miles) west of Bogota, has been on yellow alert since October 2010 and began spewing ash and smoke last week.
The director of the Manizales seismic observatory, Gloria Cortes, said they are keeping a close eye on the volcano and monitoring seismic activity as they work with local officials to ensure the safety of nearby residents and tourists in the area.
"The local committee leaders, led by the area mayors, and given the current state of activity, have made a decision regarding the level of alert for the different areas and cities," Cortes said.
Authorities from cities in the volcano's proximity say they too are carefully watching the situation and have issued green and yellow alerts depending on how close they are to the volcano.
The mayor of Manizales, Jorge Eduardo Rojas, said his city is on green alert for now adding that could change if activity increases.
"Everyone needs to be ready for any situation. However, the city alert, which is at green, is still green and is not going to change though we are of course carefully watching for any changes on Nevado [del Ruiz]," Rojas, said.
Other cities closer to the crater are on an elevated yellow alert, though they say populated centers are not in imminent danger at the moment.
Thus far, the smoke plume has not caused any problems for air traffic.
The volcano's yellow alert means an eruption is possible though not definite. If it passes to orange it signifies an eruption is likely in weeks.