CAIRO -- Protesters retook control of Tahrir Square late on Saturday after a protracted series of clashes with security officers armed with tear gas and rubber bullets. But as it approached 11:15 p.m. local time, police had begun to move back into the area in force. And rumors ran rampant that police officers from the much detested Ministry of Interior were gathering at various entrances to the square.Up a side street to the west, in the direction of the Interior Ministry, bouts of rock throwing and tear gas firing continued.