U.S. officials have been keeping migrants from crossing bridges. Now, Mexico is doing the same.

REYNOSA, Mexico — It was the third time Ingrid had tried to make it across an international bridge into Texas.

The first time, she said, Mexican officials stopped her on the bridge into Laredo and demanded that she pay $1,500 for her and her two children to cross into the United States, where she planned to seek asylum.

A few weeks later, they barred Ingrid — a Mexican permanent resident born in Guatemala, with Mexican-born children — from passing the turnstiles to cross the bridge into Hidalgo, threatening to deport her and rip up her documents.

And on Tuesday, a Mexican officer in a beige uniform sprinted after Ingrid as she walked past the turnstile and up to the midpoint of that same bridge, which spans two nations grappling with their own influx of Central American migrants.

“Can I see your documents?” the officer, Alejandro Vargas, asked Ingrid, maneuvering his body in front of her. “I need to see your documents. It’s the orders from my boss.”

Ingrid, who declined to give her last name to protect her safety, said Mexican authorities later told her that if she attempted to cross the border again, her Mexican residency would be stripped and she would be deported to Guatemala.

It’s a move immigration lawyers say is becoming increasingly common along Mexico's northern border following months of shifting U.S. immigration enforcement strategies that have prevented some migrants like Ingrid from entering the United States to seek asylum. This time, it’s Mexican officials who are cracking down.

Earlier this year, U.S. officials started turning migrants away before they could even reach the U.S. side of the bridge, telling them ports of entry were full. On one bridge, U.S. Customs and Border Protection even erected a physical structure on the invisible line between the two countries. But after asylum-seekers started camping out on the Mexican side of the bridges — sometimes sleeping on cardboard for days at a time — Mexican officials began blocking Central American migrants from entering those bridges at all.

“Before, if someone was illegally on the border, and there was a suspicion that they were going to leave the country, [Mexican immigration officials] would turn a blind eye,” said Isauro Rodríguez, an immigration lawyer based in Reynosa. “Now, they’re actually clamping down as hard as they do in other parts of Mexico.”

Advocates and lawyers on both sides of the border have various theories as to why Mexican officials are suddenly cracking down on asylum-seekers. Some believe the Mexican government is trying to save face politically, as U.S. officials question why Mexico isn't doing more to stem the northern flow. Others argue Mexican immigration authorities are under the thumb of cartels, which want to force migrants into costly smuggling rings.

Rochelle Garza, a lawyer based in Brownsville, has filed a petition with the Inter-American Commission on Human Rights asking for Ingrid and a dozen others in similar situations to be allowed to cross international bridges to seek asylum. The migrants have a right to leave Mexico and the right to seek asylum in the United States, she said, and neither country is cooperating.

Mexican migration officials declined to comment for this story.

But Hector Hugo Alemán Pacheco, an official with Mexico’s National Institute of Migration, said in a letter responding to inquiries from lawyers that allowing immigrants free entry across the bridge into the United States would mean telling Mexican migration authorities to ignore their mandated responsibilities.

“Individuals who enter or exit national territory must do so complying with immigration law and its regulations,” he said, “with intervention from migration officials.”

The petition Garza filed with the human rights commission accuses U.S. officials of asking their Mexican counterparts to ramp up enforcement. An affidavit signed by Jennifer Harbury, a Mercedes-based lawyer who accompanied Ingrid onto the Hidalgo bridge twice, said she was told by Mexican officials that the U.S. Border Patrol had instructed them to apprehend migrants. She said in some instances, Central American asylum-seekers reached the midpoint of bridges, only to be stopped by U.S. officials and told to sit down on the Mexican side. Then, Mexican officials would arrive to question the migrants.

A spokesperson for Customs and Border Protection declined to comment for this story, instead pointing to previous statements that say the agency is “not denying or discouraging” migrants from seeking asylum: “Depending upon port circumstances at the time of arrival, individuals presenting without documents may need to wait in Mexico as CBP officers work to process those already within our facilities."

The increased immigration enforcement by Mexico means it's becoming increasingly difficult for asylum-seekers like Ingrid to ask for asylum the "right" way — by crossing into the United States at an official port of entry.

She could stay on the Mexican side of bridge, hoping for another chance to cross. But Mexican officials could apprehend her for loitering in a federally controlled area.

She could pay a smuggler to take her across the Rio Grande illegally. But Ingrid doesn't have the money.

It's even riskier for migrants who — unlike Ingrid — are in Mexico illegally and could be deported at any time. Rodriguez, the Reynosa lawyer, said while migrants can theoretically appear before a Mexican judge to ask for an amparo, a kind of temporary reprieve from deportation, costly legal fees prevent them from doing it.

“What other choice do these individuals have if they’re being forced back into Mexico, where they’re being picked up by cartel members, where they’re being extorted?” asked Garza, the Brownsville lawyer.

Editor's note: The Texas Tribune and TIME have partnered to closely track the family separation crisis at the U.S.-Mexico border. This story is not available for republishing by a national news organization until Oct. 12 at 6 a.m. Texas news organizations may run it at any time. For more information email nchoate@texastribune.org.