Mexico’s government says 150,000 migrants pass through the country every year hoping to reach the United States.
Human rights groups put the number close to 400,000.
Most of the immigrants come from Guatemala, Honduras and El Salvador. In Mexico, they face several dangers, including sexual assaults, kidnappings and extortions.
More than 11,000 migrants were kidnapped in Mexico in 2010, mostly in the border state of Chiapas in the south and its northwestern neighbour Veracruz.
Most of the migrants attempt their final crossing through the northern state of Tamaulipas, an area dominated by the Zetas drug gang.
A caravan of Central American mothers has begun the journey on the so-called "route of the immigrant" in Mexico in the hopes of finding their missing children.
Al Jazeera’s Rachel Levin reports from Tamaulipas, Mexico.