A new group of human remains has been uncovered on the Plain of Jars in Laos. They are believed to date back to the Iron Age, some 2,500 years ago.

The Plain of Jars is in the central Lao province of Xieng Khouang. The area covers hundreds of kilometers in which can be found thousands of ancient stone jars. They are grouped together at about 100 sites.

The Plain of Jars has been a puzzle to archaeologists—scientists who study prehistoric people and their culture.

A joint research team from Australia and Laos found the remains.

Dougald O'Reilly teaches archaeology at Australian National University. He led the field work in Laos.

"This is one of the great enigmas of the Jars' sites," he said. "These massive stone jars – some of them weighing up to 10 metric tons, that have been dragged eight to 10 kilometers from a quarry site and set up in groups."

Little is known about the people who made the jars. What did the jars hold? How and why did people place them where they did?

O'Reilly said a central question that needs to be answered is who created the stone jars. There are no known sites offering answers to the ethnicity and identity of the people who made them.

The latest field work uncovered an ancient burial ground in an area known as Site 1, in Xieng Khouang Province. It has more than 300 stone jars, stone discs and markers.

The scientists uncovered different burial methods. They include burial of whole bodies, the burying of bones grouped together, and bones placed inside ceramic vessels and then buried.

Louise Shewan of Monash University in Australia led one of the teams involved in the field work. Archaeologist Thonglith Luangkhoth, of the Lao Ministry of Information, Culture and Tourism, also led a research team.

Thonglith told Lao media the newly uncovered remains were found about eight kilometers from the center of Phonsavanh district.

"This discovery marks a significant milestone since archaeological excavations began in the area in the 1930s in collaboration with a French archaeologist," he said.

Dougald O'Reilly said the researchers hope to get really good information from the find.

"With our research, because we've been able to uncover a fair amount of human bone – we've got seven burials and four probable burials with ceramic jars – so a total of 11 mortuary contexts."

He said they are excited to have the opportunity to work at one of South East Asia's more important—and probably least understood archaeological sites.

Scientists will do isotopic and chemical tests on the remains. They may provide information on the ethnicity of the people connected to the sites.

O'Reilly said it is possible that the Lao sites may be linked to similar jar sites in India.

The Australian Research Council is paying for the project. It will continue over five years with field work in Laos and some in northeastern India as well.

The effort may soon provide answers to one of Southeast Asia's greatest cultural mysteries.

I'm Anne Ball.

Ron Corben reported this story for VOA from Bangkok. Anne Ball adapted it for Learning English. Caty Weaver was the editor.