Nancy Beavan is on the verge of a discovery. A set of ancient burial jars, a subject on which the archaeologist is something of an expert, has been sighted deep in the jungle. If she and her team can only find them, they will have another piece of a puzzle they have grappled with for more than 10 years.

On Saturday morning, Beavan set out on a days-long trek in the eastern Cardamom mountain range, where she hopes to find the 11th in a series of sites where ceramic jars were used for burials between the 14th and 17th centuries. It’s a project she has worked on since 2003.

If she reaches the site, known as Cedi, Beavan and her colleagues intend to spend at least two days inspecting, photographing and geopositioning the site, before returning for more extensive fieldwork in the autumn, and hoping that it won’t have been damaged either by natural causes or by ongoing development in the Cardamom mountains.

“The local people will probably know if they’ve been destroyed, but I’m hoping that’s not the news that we have before we can go in October or November,” Beavan said in an interview last week.

“But if I run out of time, or the sites are destroyed, at least we have the most basic recording of what was there.

“I still think that what we’ve been able to do has already changed the perception of what is the history of the people during this 14th to 17th century period.”

One of the most intriguing aspects of the burials is that the period in which they occurred coincides with the decline of the Angkorian civilisation in the north of the country and the shift of power to Mekong trading ports.

While most of the jars found in the Cardamoms have been storage jars, believed to have been made in Thai kilns, several were made in an Angkorian style, hinting at intriguing connections between the people who lived in the highland areas and those in the lowlands.

There’s no guarantee that the new site, which fits into a linear pattern of sites along a ridge line in the Cardamoms, will be accessible, or found intact. The area is mountainous and jars are often found precariously balanced on elevated ledges, according to Beavan. One of the other jar burials was found in an already damaged condition.

“When we find broken jars we don’t necessarily blame people,” said Beavan.

“It can be rock flaking, pigs trying to find shelter or wanting to eat the bone, rats gnaw the bone, termites eat the bone and there’s a lot of natural degradation.”

Villagers living near to some of the remains have a strong connection with the jars and have carried out pilgrimages. It took months of delicate negotiations with local people in the area, near to the Areng Valley, to arrange this weekend’s visit to Cedi.

Alejandro Gonzalez-Davidson, an environmental activist who has worked with the community for more than 10 years, said: “They know of other sites but they don’t want to take people.

“Once the secret is out, they’re afraid of people taking [the jars] away.”

In 2002, a group associated with the making of a National Geographic documentary took jars and placed them in a museum. Local people have been wary of foreign visitors ever since. But a big threat to the jars has been the ongoing development projects in the Cardamoms, according to Beavan.

In 2011, the decision to cancel a planned titanium mine in the region which was “snack-dab over most of the jar burials”, was a saving grace for the project, she said.

“I thought, wait, my sites are on rock, and they’re going to be prospecting the rock – that’s not a good thing!”

As a result, the archaeologist is anxious about leaving the jars alone for more than a few months. Other academic obligations will take Beavan to Europe in the summer but she wants to return to Cedi as soon as she returns.

“Why? Because as conservations have reported, there is a danger to the forest with clear-cutting and such. But along with the clear-cutting and bulldozing of access roads and such there comes a danger to the sites.”

One solution is heritage protection zones, which have already been put in place at archaeological sites including Preah Vihear. These usually consist of little more than stakes and signs marking out the area.

“You could put markers around the spot but in a place like the Cardamoms, if anything, that is drawing attention to them,” Beavan said.

“Sometimes, announcing it is not a good idea: ‘this is really valuable, and you’re in the middle of the jungle, and nobody’s watching you.’ It’s like a free buffet.”

In the case of the jars, markers have been put well away from the location. Their fate, however, is tied to that of the Cardamoms, a place Beavan believes still has much to reveal.

“It’s enormous and it’s complex and it still has so many secrets. I hope we discover some of them before it’s all gone.”