JINAN: China is stepping up work to preserve the oldest section of the Great Wall after months of investigation to determine its length and location, archaeologists said Saturday.

The Great Wall's oldest section was built between 770 B.C. to 476 B.C. in the ancient state of Qi, hence the section is often called the Great Wall of Qi.

After a seven-month investigation, the Great Wall of Qi was found to stretch 620 kilometers, from Jinan City, capital of east China's Shandong Province, to Qingdao, a coastal city of Shandong, said archaeologist Li Zhenguang, head of the investigation team.

The results laid the foundation for the preservation of the Great Wall of Qi, which had constantly been damaged by local residents, he added.

After identifying the exact length and location of the entire Great Wall, a system can be established to hold local governments to account for vandalism, Li said.

The investigation is part of a plan to better preserve the Great Wall by the State Administration of Cultural Heritage.

According to the plan, China's knowledge of the Great Wall is very limited and many parts of it need to be explored before a comprehensive database can be built to better preserve it.