(AP) — Another group of some 200 migrants has started walking north from the southern Mexico city of Tapachula despite a heavy presence of National Guard troops and immigration agents. The Mexican forces have been dispersing similar groups in recent days, including several hours before the latest band started out Wednesday. Authorities lately have allowed groups of migrants to walk for hours and tire under sweltering heat before swooping in to detain them. Before dawn Wednesday, authorities surprised migrants sheltering from the rain in Mapastepec, chasing them between houses and businesses. The enforcement efforts follow an encounter over the weekend when The Associated Press and other media outlets filmed immigration agents kicking a migrant who was already on the ground.