Phase II is defined by a larger population and definitive evidence for the mass production of rice. The borders of the site expanded during this period (possibly covering 100,000 square meters or more). Other developments include the presence of permanent mud brick architecture, including a city wall, probably built during the latter half of the first millennium AD using the cylindrical brick technology, "which was 3.7 meters wide at its base and ran almost two kilometers around the town". It is inferred from this that rice domestication might have led to higher population, or higher populations led to the domestication of rice in this period. Phase III dates from about A.D. 300 to A.D. 900 and is believed to have an even higher population based on crowded cemeteries. The site also has evidence for a more intensive occupation through deep house deposits, possibly from multiple generations. Since there is no evidence for a fourth phase, it is expected that towards the end of Phase III the city experienced a slow decline in population and eventually a total abandonment. However, very little is known about why this decline happened, and more research is needed.