Roberto Hernandez Velasquez, a backpack of personal belongings weighing him down, heads north on a railroad track frequently traveled by migrants from around the world as they make their way to the United States.
With his rumpled and dirty clothes, Mr. Hernandez looks as if he could be one of the tens of thousands of migrants who pass through this section of southeastern Mexico every year. But he is not. Nor are the other armed young men following him.
Hernandez is a decoy. He and the men following him are part of a recently created squad of police on Mexico's southern border whose job is to make sure the rights of migrants are protected and to try to reduce the crime and abuse that befall them.
"On this operation we're trying to flush out members of gangs we know operate in this area and prey on the migrants," whispers Israel Gallegos Sierra, a supervisor with the squad, called Beta Group South.
The group, modeled on existing migrants-rights squads operating on Mexico's northern border with the US, is part of a campaign to improve the treatment of migrants in Mexico. The 20 squad members, culled from the best performers of various police corps, talk with migrants, pass out a new government pamphlet that explains migrants' rights, and hunt criminals.
The group working the railroad track meets a group of Central American migrants who have been arrested by immigration police and are waiting to be returned to the Guatemalan border.
They don't, however, arrest the migrants, although traveling through Mexico without proper documents is illegal. "That's for the immigration police," says Mr. Gallegos. "We want [the migrants] to trust us."
That attitude does cause friction between the Beta police, who have been on the job for less than two months, and their immigration counterparts. "There is some mistrust. Some of them complain that we are working at cross purposes," Gallegos says. "And every once in a while you hear one [of the immigration police] speak of 'the good old days' of impunity, when they could make some money. But that's a small minority."
The Betas - who earn a $250 monthly bonus for joining the squad - do not apologize for their work. If anything, they aspire to match the level of recognition earned by the Tijuana Beta Group, which last year was cited by the National Human Rights Commission as the most honest and efficient police organization in the country.
Assaults on migrants in the far southwest of Mexico are down this year. But Tapachula district immigration chief Raul Morales says that cannot yet be attributed to the Betas. "What's happening is that with the stepped-up surveillance we have along the border, the migrants are being pushed out to more remote areas, and that's where the delinquency is occurring now," he says.