Colombia's biggest coal exporter Cerrejon [joint venture Anglo American, BHP Billiton, Xstrata] said...that four contractors had been killed and 12 others injured while repairing a coal-storage silo...Colombia is the world's fifth largest coal exporter and Cerrejon...has an opencast mine that is the biggest in the world. "There was an unfortunate accident (on Wednesday night)... a group of sixteen workers from the contracting companies Conconcreto and Ticom were standing on a high platform when it collapsed," Cerrejon said in a statement.