With the Mexican government struggling to contain crime and violence, and ramshackle camps full of vulnerable migrants cropping up on the border, kidnappings have spiked. “Families on this side of the border, regardless of social status, will manage to pay ransom,” said Octavio Rodriguez, a scholar at the University of San Diego who studies violence in Mexico and the border region.

The authorities have doubled the number of police officers in the past three years in the state of Tamaulipas, which includes Reynosa, but it is not enough, said Aldo Hernandez, the state’s communications director. “Neither the municipal nor state governments have the resources to fight this situation,” he said.

Some are blaming Mexico’s president, Andrés Manuel López Obrador, and his government’s decision to step back from confrontations with drug cartels.

“The López Obrador administration has sent the message to organized crime that police and national guard will not confront you. That emboldens them to target this population,” said Tony Payan, a scholar at the Baker Institute of Rice University who studies the United States-Mexico border.

Mark A. Morgan, acting commissioner for Customs and Border Protection, said that those awaiting asylum hearings who fear for their safety should “work with the government of Mexico” to keep themselves safe.

“I have heard reports the same as you of violence,” he told reporters last week, noting that it is well known that dangerous drug cartels target migrants south of the border. “We encourage these people first of all not to even put themselves in the hands of the cartels to begin with.”

In the border towns of the Rio Grande Valley, the busiest migrant crossing point into the United States, kidnappers have struck in recent months near shelters, at bus stops and outside grocery stores.