By Amitabha Bhattasali
BBC News, Calcutta
Archaeologists in the eastern Indian state of West Bengal have discovered small weapons made of stone which are around 15,000-20,000 years old.
Stone age weapons are not usually found in such an old soil layer
The artefacts - dating to the Stone Age - were found during excavations in Murshidabad district, near Bangladesh.
Archaeologists say the find is potentially significant as it suggests man's presence in the area dates back much earlier than previously believed.
Finds such as this on the floodplains of the River Ganges are very rare.
However, there is ample evidence of stone age activity in India's upland regions.
The weapons - which include small axes - were discovered at Ekani-Chandpara village near Sagardighi, which is an ancient site.
This is one of a number of pots found at the site
Archaeologists say the weapons were found from a soil layer belonging to the mid-Pleistocene period - much below the Holocene layer where present human habitation takes place.
"We have not only discovered the weapons at this site, but raw materials and the scraps were also found," Dr Gautam Sengupta, director of the State Archaeology Department, told the BBC.
"This proves that the weapons were made at this place itself."
Another reason why the find is so significant, archaeologists say, is because Stone Age weapons are not normally found at such an old soil layer in the Gangetic alluvial plains.
However it is well known that raw materials for making weapons are easily found in the plateau region and most Stone Age discoveries are from this area.
So far, no human fossils or remains other than some charcoal have been found at the site.
Scientists have yet to confirm how old the charcoal is.
The archaeologists were surprised by what they found
"The history of civilisation in this region has suddenly gone back by around 20,000 years," one archaeologist said.
After the discovery, two eminent geo-archaeologists - Prof SN Rajguru and Dr Bhaskar Deotare - visited the excavation site and confirmed that the weapons date back to the smaller Stone Age.
The discovery was made by chance, Dr Sengupta said.
"We were digging the site for some archaeological evidence of the Sultanate period. We were expecting some ancient artefacts related to Sultan Hussein Shah," he said - referring to a former ruler from the area.
"We did find those, but our archaeologists kept on digging to unearth some more historical evidence of that period and now we have found these Stone Age weapons," Dr Sengupta said.
After winding up the excavation at Ekani Chandpara in a couple of weeks, archaeologists are planning to launch a search for ancient human habitation in a wider area.