Relics unearthed in Yuen Long provide evidence of human activity there 4,000 years ago, the Antiquities and Monuments Office said yesterday. An archaeological survey carried out in 1997 and last year unearthed another 30 historical sites, bringing the total number to 207. The new sites are in Deep Bay, Yuen Long; west of the Tuen Mun River; So Kwun Wat; Ma On Shan; Pak Sha Wan, Sai Kung; and the Lam Tsuen Ho basin in Tai Po. The office was particularly excited about the discovery of prehistoric sand dunes and hillocks on the coast at Deep Bay, which could date to the late neolithic period. Curator (archaeology) Chau Hing-wah said: 'Those sites are well-preserved and have not been damaged by the town development. 'Moreover, the size of the sites are enormous and their cultural accumulations are plentiful. 'Their discovery proves there were some primitive tribes settling along the coast of Deep Bay about 4,000 years ago.' The survey also found the well-preserved remains of a 300-year-old blue and white porcelain factory in Tai Po, which only ceased production at the beginning of this century.