MEXICO CITY (Reuters) -A 2014 toxic spill in a Mexican river blamed on Grupo Mexico was not an accident but a result of negligence, the country's environment minister said on Thursday, while urging the mining conglomerate to create a new plan to remediate the damage. "It was not an accident, it was negligence," Environment Minister Maria Luisa Albores said, adding that the government filed a complaint in August against the company, one of the world's largest copper producers. Grupo Mexico failed