Luis J. Jimenez for The New York Times
Mexico has its own immigration problems. An illegal immigrant from Cuba, center, in a cell in Tapachula, is among those awaiting deportation.
"A migrant with money can make it across Mexico with no problems," Father Barilli said. "A migrant with no money gets nowhere."
Mexican law authorizes only federal migration agents and federal preventive police officers to inspect cars for illegal migrants and to demand proof of legal status. But Mexican authorities acknowledge that migrants face run-ins with every level of law enforcement.
Migrants are also routinely detained by machete-wielding farmers, who extort their money by threatening to turn them over to the police. So many female migrants have been raped or coerced into sex, the authorities said, that some begin taking birth control pills a few months before embarking on the journey north.
Few are punished for such crimes, the authorities added, because the migrants rarely report them.
"This society does not see migrants as human beings, it sees them as criminals," said Lucía del Carmen Bermúdez, coordinator for a government migration agency called Grupo Beta. "The majority of the attacks against migrants are not committed by authorities, although there is still a big problem with corruption in Mexico. Most violence against migrants comes from civilians."
Grupo Beta is a uniquely Mexican creation; established 16 years ago in Tijuana to protect migrants. It was a time, said Pedro Espíndola, the director of Grupo Beta, when Mexican migration to the United States began to soar, and smuggling groups evolved from small-time, community-based operations into transnational criminal cartels.
Grupo Beta was expanded to the southern border in 1996, Mr. Espíndola said, when throngs of Central American migrants, aiming for the United States, began hopping freight trains in Tapachula. Train stations became easy staging areas for gangs to ambush migrants. Hospitals became overwhelmed with men and women who had fallen beneath moving locomotives, often losing limbs to their wheels.
Last year, Grupo Beta reported, 72 migrants died crossing the southern border, mostly in accidents on trains or highways. Human rights groups say the real figure is more than twice as high. And in the 16 years since one woman, Olga Sánchez Martínez, began selling bread and embroidery to operate a shelter and then a clinic for migrants, she said, she has treated more than 2,500 migrants with machete and gunshot wounds or severed limbs.
Last year's rains did so much damage to the bridges and roads around Tapachula that the train does not stop here anymore. But that has not stopped the migrants.
Some detour north of here, the authorities said, to train stations that run through the state of Tabasco. But migrants like Mr. Godoy, the Honduran, have so far refused to abandon this route. He walked eight days along the tracks that run from here to the station in Arriaga, about 120 miles away. Then he, along with at least 300 others, hopped a freight train that leaves there almost nightly, in plain view of evening traffic, the local police and the train's engineer.
It was Mr. Godoy's third attempt in three months. He said he had been caught by United States Border Patrol officers in Laredo, Tex., on each of his previous trips.
"I am not going to give up," he said. "I had a good life in Miami. I got no criminal record. I never hurt nobody. I'm just trying to be with my kids, you know? That's all I need."
Correction: June 20, 2006
An article on Sunday about the difficulties Mexico faces in policing its southern border referred imprecisely to a southern state where Mexico has immigration agents. Yucatán is near the border but not on it.
Luis J. Jimenez. for The New York Times
Eduardo Esobar, a Salvadoran migrant, hopped a train in Arriaga, Chiapas. He said he was headed to the United States to search for work.