Members of the Vietnam Archaeological Institute and the Bac Kan Museum have been excavating the area for possible prehistoric remains since early June. 

Na Mo Cave is situated in Na Ca hamlet, Huong Ne commune, Ngan Son District. The 15m high and 500m wide cave is in the side of the limestone mountain and looks out over a large river valley. Most of the surface of the cave can get sunlight, making it favourable for habitation. 

Stone artefacts dating from 20,000 BC to 10,000 BC have been found in the cave, including simple working tools made from pebbles found in the river nearby. They have characteristics of tools dating back to the Hoa Binh culture. 

Archaeologists have also unearthed pottery objects made by hand and decorated with designs. Traces of cooking fires are also uncovered, along with thick coal seams and burned red soil. A large quantity of animal teeth and bones and the snail and oyster shells are also discovered. 

Experts are able to affirm that the prehistoric cave dwellers lived on hunting and gathering. They are able to cut hunted animals into parts and grill them over the fire. 

They also found a kind of red stone used to grind pigment powder for decoration. 

They excavated a tomb containing the bones of a person who had been buried with a stone tool. 

The head of the exploration group, Trinh Nang Chung from the Vietnam Archaeology Institute, said Stone Age people inhabited the area for many thousands of years and are responsible for what has become known as the Hoa Binh culture around 10,000 BC. 

In July 2011, traces of prehistoric man are also found near Ba Be Lake in the northern province of Bac Kan.