While reporting this story last week among the down-and-out (and recently deported) at a migrant shelter in Tecate, Mexico, I met a few men who had a whole new reason to dread re-arrest by U.S. Border Patrol.

They were trying to sneak back into California. But if caught, they were likely to be transported hundreds of miles east by U.S. immigration authorities, where they would be released onto the streets of some of Mexico's scariest border towns.

The procedure is known as Lateral Repatriation, or Lateral Deportation. It began a decade ago as a pilot program aimed at reducing migrant deaths in the blazing deserts of Arizona. The thinking was this: Instead of sending illegal migrants back to the Mexican side near their point of arrest, U.S. agents could break the catch-and-release pattern — and ties to local smuggling guides — by shipping deportees from the harsh deserts to more settled areas opposite south Texas.

An illegal migrant apprehended in the mountains outside Nogales, Ariz., for example, could be processed and transferred by bus or flight to Brownsville, Tex., and expelled to the Mexican side there.

Depending on your view, this was either a humane gesture designed to protect the deportees or a cynical way to make a tough journey even tougher.

Only now, the Lateral Repatriation program is potentially exposing migrants to new dangers, by dumping them off in Mexican border towns stalked by criminal gangs and kidnapping crews.

The deportees in the Tecate shelter expressed an especially pronounced fear of being sent back to Nuevo Laredo, the border’s busiest commercial port. It’s also the stronghold of the savage Zetas drug cartel, which massacred 72 migrants in August 2010 — most of them from Central America — and has dumped untold others into mass graves.

Even as violence has increased in Mexican border states such as Tamaulipas and Coahuila, U.S. authorities have increased the number of deportees they’re sending to those places, according to a new study by Maureen Meyer and Adam Isacson at the Washington Office on Latin America (WOLA). They found an apparent correlation between homicides in a Mexican border zone and the number of deportee arrivals.

“A review of data from Mexican security and migration authorities reveals a troubling trend: As border zones become less secure, they receive more deportees,” they write. “In every Mexican border state that saw an increase in homicides since 2009, deportations from the United States also increased. In Mexican states where homicides declined, deportations also declined."

“These data don’t indicate something as nefarious as U.S. migration authorities deliberately placing deportees in harm’s way,” they continue. “However, the numbers do indicate that U.S. migration authorities either aren’t taking security risks into account when they deport people, or if they are, that they are not even close to keeping up to date on Mexico’s shifting patterns of violence.”