Bolivia borders Brazil, the second biggest consumer of illegal drugs in the world; Peru, the world's top producer of cocaine; and Paraguay, South America's primary producer of marijuana.
Forty-three students disappeared late last month after a confrontation with police. Many fear that Mexico's grim record of impunity will thwart an investigation into their fate.
If the newly discovered burial site holds the remains of the 43 students missing after a confrontation with police last weekend, this would be the nation's worst known massacre since President Peña Nieto took office.
Brazilians head to the polls Sunday to vote for their next president. Marina Silva raised hopes for reform when she entered the race, but her flip-flopping on issues like gay rights has many flocking back to the ruling Worker's Party.