The Chinese pilgrims Xuanzang and Yijing mentioned Sri Ksetra in their mid-7th-century accounts. It is not known when precisely the Pyu abandoned Sri Ksetra and moved northward. It is speculated that their decline was due to the growth of the Irrawaddy river delta, cutting it off from coastal trade, and also from Mon and later Tai Shan incursions. Burmese chronicles state that when Anawrahta invaded the southern parts of modern-day Myanmar in 1057, he ordered the ruins of Sri Ksetra to be destroyed to prevent rebels from sheltering there. The Burmese came to call the old Pyu center Pyi. The extensive ruins have been the subject of intensive archaeological investigation.