Most likely the same problem that affected some Bolivian track several years ago. Someone stole several hundred meters of track near Oruru, Bolivia on the FCA. A southbound train derailed because the engineers could see the missing track at night. It took some real planning to steal that much heavy steel without somekind of mechanical help.
Stealing track and anykind of scrap is big business for scavangers these days. Most of the Guatemalan rail system has been stolen and bridges partially robbed of easy steel scrap.
Dale Brown