TAIYUAN -- Archaeologists have found ruins of a pentagonal structure believed to have been a tribal meeting hall or a leader's office from 6,000 years ago, authorities in North China's Shanxi province said Monday.

The semi-subterranean house, discovered at the Neolithic ruins at Taoyuan, a village in the city of Linfen, covered a total area of 90 square meters, with surviving walls reaching a maximum of 50 cm, said Xue Xinming, a researcher with Shanxi provincial institute of archaeology.

The walls were painted with a mixture of grass and mud inside, and several holes were also found where wooden pillars were located to support the house and walls, said Xue.

A cylinder-shaped fireplace was also found underground in the house, which ancient people used for heating, cooking and lighting.

According to Xue, the pentagonal building was rare for that period as the prehistoric people only built structures larger than 80 square meters in the shape.

"Such a big building perhaps was an office for a tribe leader or a public venue for meetings or worship ceremonies of a major tribe," he said, adding it was the first of its kind found in Shanxi Province.

Previously, a dozen prehistoric pentagonal buildings had been found in China, mainly located in Lingbao City, Henan Province.

The discovery is part of findings from an excavation that began in August in Taoyuan, a village in Jiade Township of Linfen's Yaodu District, to prepare for highway construction in the area, said Zheng Yuan, excavation team leader of the project.

Zheng said the total excavation area is 2,500 square meters, and aside from four house ruins, they have also discovered ruins of a pottery kiln and unearthed a variety of pottery pieces.

She said the excavation is important for researching society and life in the Miaodigou Culture, the most powerful period in prehistoric China, which was centered around the provinces of Shanxi, Shaanxi and Henan.