<p>The leader of a criminal gang suspected of conspiring with Mexican police to kill 43 missing students in the violent southwestern state of Guerrero has been detained, authorities said on Friday.</p>
<p>The students went missing near Iguala, Guerrero on Sept. 26 after clashing with police and masked men, sending shockwaves across Mexico and prompting thousands to march in the beach resort of Acapulco on Friday to demand answers about their fate.</p>