In a press release, the department said the investigation team were inconclusive about the smoke emitting from the mountain near the Vishepu village.
It further said the smoke could be the result of a normal process of water condensation or due to chemical reactions within the rocks or seasonal periodic change of atmospheric pressure and climate change.
The department also undertook an aerial survey as well as an on-spot inspection of the phenomena on the Khumnubato range southwest of Vishepu village and collected rock, soil and water samples for laboratory analysis for a final conclusion.
''The mountain range is made up of sedimentary rocks of mainly calcareous rich shale, siltstone and sandstone with thick vegetation covers,'' the release said.