A migrant rests at the Migrant House in Arriaga, Mexico, Thursday. A caravan of activists highlighting migrants' rights were to board a cargo train there Friday. ((Miguel Tovar/Associated Press))

A group of human rights activists highlighting violence against migrants travelling through Mexico were to jump aboard a cargo train in the country's south on Friday, led by a Catholic priest.

The activists hope to draw attention to the dangers faced by South and Central American migrants passing across Mexican territory on their way to the United States. Many are kidnapped for ransom by drug traffickers. The kidnappings have turned into a multimillion-dollar business and the migrants often end up killed.

The caravan of activists will begin in Arriaga, Chiapas, the southernmost point in Mexico's railway system, where they will board a cargo train known as "the Beast." Tens of thousands of Central American migrants clamber aboard the train each year, riding on top of and between the cars on their way to the United States.

Temperatures atop the metal boxcars can range from freezing cold to searing heat, and a fall from the train can lead to loss of life or limb. 

Rev. Alejandro Solalinde, who runs a migrant shelter in Ciudad Ixtepec, Oaxaca, is leading the activists. One of their aims is to encourage those who live along the railway to report crimes against migrants instead of ignoring them, he said.

At least 40 Central Americans kidnapped last month in Oaxaca remain missing. The kidnappings have been attributed to the Zetas drug cartel, the same organization suspected of massacring 72 migrants last August in the northern state of Tamaulipas.

Data published by Mexico's National Human Rights Commission shows an average of 50 migrants are kidnapped each day in national territory. Most of these crimes occur in southern Mexico.