How Mexican cartels manage the flow of migrants on their way to the US border

CIUDAD HIDALGO, Mexico (AP) — The first place where many migrants sleep after entering Mexico from Guatemala is inside a large structure, a roof above and fenced-in sides on a rural ranch. They call it the "chicken coop" and they don't get to leave until they pay the cartel that runs it.

Migrant encounters at the U.S.-Mexico border have reached a four-year low, but days before the U.S. election, in which immigration is a key issue, migrants continue pouring into Mexico.

While U.S. authorities give much of the credit to their Mexican counterparts for stemming the flow to their shared border, or...