bogota least six farmers protest removal coca crop base ingredient cocaine kill confrontation rural southwestern colombia president juan manuel santos say friday santos order investigation event take place thursday also injure 19 people incident occur narino province near tumaco key zone coca grow report exactly six people die contradictory defense ministry say thursday dissident group ex-fighters revolutionary arm force colombia farc rebel group force farmers protest police remove coca crop dissidents fire officer launch home-made missiles hit farmers ministry say regional farmers organizations accuse police army fire civilians break protest clear way manual eradication crop majority farc fighters demobilize peace deal sign last year dissident units remain involve drug traffic illegal mine farc political party distance dissidents verify exact way things occur santos say press conference investigate want tie version events investigations give us total clarity happen events underline significant challenge drug trade represent peace process farc head unite nations mission colombia say events reinforce conviction unite nations necessity give coca farmers affect regions mean escape terrible choice extreme poverty illegality mission chief jean arnault tell journalists subsistence farmers often oblige rebel group paramilitaries crime gang plant harvest coca also choose grow crop illegal group pay farmers earn market products tempt possibility amid dire poverty coca cultivation reach level see decade last year government ban aerial fumigation glyphosate herbicide link cancer prohibition spark criticism unite state set give andean country 400 million fund help farc deal coca cultivate 188,000 hectares 464,000 acres across colombia government want manually eradicate 100,000 hectares year least six die colombia protest coca crop removal