A woman buys from a street vendor near a sign showing the direction to the Mathari Mental Hospital on May 13, 2013 in Nairobi. Kenyan police have launched a manhunt for 40 mentally ill patients who escaped from a psychiatric hospital in the capital Nairobi, officials said Monday. The patients overpowered guards and forced open the door of their ward in the Mathari Mental Hospital on Sunday morning, said local police chief Samuel Anampiu. At least 35 others were stopped by guards from leaving after the initial breakout. The hospital lies close to the sprawling Mathare slum district of Nairobi.