ZHENGZHOU, March 9 (Xinhua) -- Chinese archeologists have identified the route of a 137-km stretch of China's oldest Great Wall in central Henan Province, on which the remnants of 30 km of wall is still standing.

"The wall structure was built no later than 221 B.C. in the Warring States period," said Sun Yingmin, spokesman of the provincial Cultural Relics Bureau, Tuesday.

He said previous to this, only sporadic discoveries of wall remains were found. The actual appearance of the main body of Great Wall of the Chu State was only recorded in historical records.

Sun said an archeological survey since 2008 led to the finding of the Great Wall structure, which runs mainly east to west, spanning 25 counties and districts in the province.

Emperor Qin Shi Huang, who reigned from 247 B.C. to 210 B.C., has long been credited with building the Great Wall. Actually, he linked up the different sections of the wall built by different states during the Warring States Period. Construction and repairs continued from the Qin to the Ming Dynasty (1368-1644).

Historical records show as early as the Spring and Autumn Period, Chu, one of the seven major powers, had constructed the Great Wall to prevent invasion from the northern states such as Wei.

Sun said the research in Henan proved most parts of the Great Wall of Chu had been built in the Spring and Autumn Period (770-476 B.C.), and small parts built in the Warring State Period (475-221 B.C.).

He said remnants of the wall exist in Henan and Hubei provinces. During the survey in Henan, archeologists excavated two Great Wall fortresses, and three ancient town sites.