HOHHOT, May 2 (Xinhua) -- Illegal excavations have left a dozen holes under a section of Qin Dynasty Great Wall built over 2,000 years ago in north China's Inner Mongolia Autonomous Region.

Police in Guyang County, Baotou City, said on Wednesday that they have arrested two thieves who allegedly dug for relics such as coins and arrowheads along the Great Wall.

Inner Mongolia boasts a 7,570-km stretch, or 35 percent of the Great Wall.

Police investigation found that the suspects bought metal detectors to search for underground relics and dug into the soil around the wall.

The wall, built on mountain ridges, has a beacon tower every 1,000 meters in Baotou. The suspects were caught by police while they were digging around one of the towers. Police seized a number of relics on the spot. Most of the stolen items have been retrieved.

The illegal excavation was reported by volunteer guards. The county has 45 such volunteers.