Dozens of megalithic jars have been discovered in Assam, India, at four new sites, a new study published in the Asian Archaeology journal has found.
Ranging from one to three metres tall, some of the jars have decorative carvings and others are plain, according to the study coauthor Nicholas Skopal, a doctoral candidate at Australia National University in Canberra.
Whilst 65 jars have been identified so far, it's thought many more could be buried underground.
It's still unknown where they were made and which civilisation used them.
Before Skopal's 2020 excavation, the "megalithic" (meaning big standing stone) jars had been found on seven known sites, and Brits had discovered some near the Assam site in the 1920s.
When excavating the areas surrounding three of these sites, they discovered four more sites with partially exposed jars.
Skopal told CNN : "By going out, surveying and documenting them properly, the government and universities can manage their heritage a lot better and preserve these jars for future generations."
But when the research team found the jars, the majority of their contents had disappeared.
There are oral historical accounts of the Naga, local villagers, pulling beads and other items out of the jars - and some locals still have the beads as family heirlooms.
"In one of the villages we're staying in, one of the elderly ladies actually showed me (some jewellery) that had been pulled out of the jar," he said.
In Laos, similar types of jars have been excavated, with artefacts still contained inside such as beads and human remains.
Skopal hopes his team will soon find some unopened jars at the new sites in Assam.
He said: "Some of the buried ones might have things still inside, but we haven't excavated yet."
To understand when the artefacts were buried, Skopal's team intends to use optically stimulated luminescence or OSL - a dating method which involves taking a sediment sample from directly underneath the jar, to determine when the light last hit it.
The date would indicate when the the jars were buried, helping archaeologists to better understand exactly when the jars were created.
