The search engines of two of the most popular Web portals on the mainland, Sina and Sohu, were forced to close noon Monday after an on-the-spot censorship test found they had failed to filter certain keywords deemed politically harmful, the South China Morning Post reported. The two portals were given three days to "rectify their mistakes", industry sources in Beijing said, at which point they are expected to reopen. The search engines carried a message that the sites were undergoing upgrades.