At least five people are killed in the Mexican state of Michoacan after gunmen launch a grenade attacks on federal police.br br Mexican authorities say police responded with gunfire killing five gang members and injuring five officers.br br Gunmen littered streets with burnt-out vehicles as gang members opened fire on police. Authorities have not confirmed if any police were killed.br br They also attacked a hospitalbr br Drug violence in Mexico has killed more than 55,000 people since December 2006.