Migrants trying to illegally enter the United States through Mexico say that they face more danger from drug cartels than immigration enforcement, highlighting the scale to which criminal groups are able to prey on the constant flow of poor and desperate people moving through their territory.

Speaking from a shelter in the Mexican border city of Matamoros, a migrant traveling from Honduras to the US told The Associated Press that the journey was difficult "not so much because of Border Patrol" but because of the drug cartels.

The threat is so great that migrants staying at the Matamoros shelter are asked to leave during the day. Otherwise, when grouped together, they are viewed as easy pickings for criminal groups operating in the area, according to one person who worked at the refuge. The staff member recounted one incident in which armed men kidnapped 15 people from the shelter in a single night. At other times, staff members have had to eject suspected members of criminal groups who'd infiltrated the refuge in order to recruit volunteers.

InSight Crime Analysis

Migrants attempting the dangerous journey from Central America and Mexico into the US are a natural target for criminal organizations, who exploit their desperation and vulnerability in numerous ways.  Asides from running their own human smuggling networks, criminal groups like the Zetas are known to have extorted "coyotes" and migrants who move through their territory, or "plaza." Migrants also face the threat of being kidnapped, or being forced to work as drug mules or perform other jobs for the cartels

Criminal organizations are not the only threat facing migrants. There are some documented cases of Mexican immigration officials selling migrants to criminal groups

Resistance is met with violent reprisals -- "You pay or you die," said a kidnapped and tortured migrant describing his experience to NPR in 2011. In one infamous massacre, 72 migrants were slaughtered by the Zetas in Tamaulipas in 2010 - a massacre that was followed by the discovery of a series of mass graves in the same state the following year, in which more than 200 bodies believed to have been migrants were recovered. According to the AP, around 70 bodies of migrants were discovered by authorities in the Rio Bravo region, adjacent to Matamoros, during the first six months of this fiscal year, more than double that of the same period last year.