MATAMOROS, Mexico >> A smoke-filled stench fills a refugee camp just a short walk from the U.S.-Mexico border, rising from ever-burning fires and piles of human waste. Parents and children live in a sea of tents and tarps, some patched together with garbage bags. Others sleep outside in temperatures that recently dropped to freezing.

Justina, an asylum seeker who fled political persecution in Nicaragua, is struggling to keep her 8-month-old daughter healthy inside the damaged tent they share. The baby, Samantha, was diagnosed with pneumonia and recently released from a hospital with a dwindling supply of antibiotics.

“I face cold, hunger and everything because I don’t have resources, and my daughter doesn’t either,” said Justina, who didn’t want her last name used out of fear for her safety.

The camp is an outgrowth of the Trump administration’s “Remain in Mexico” policy, which has sent more than 55,000 migrants, including Justina and Samantha, south of the border to wait and pursue their asylum cases.

A humanitarian crisis is worsening each day at the camp across the border from Brownsville, Texas, where a large American flag flapping in the wind is visible from more than 700 tents. As many as 2,000 immigrants are waiting for U.S. court hearings amid deteriorating medical and sanitary conditions.

Safe drinking water is scarce. People regularly line up for a half-hour to fill milk jugs and buckets with water. Some people bathe and wash their clothes in the Rio Grande, known to be contaminated with E. coli and other bacteria. They rely on donors who bring meals, or they pull fish from the river and fry them over wood fires.

Near the wooden toilets, the air smells like feces. Flies buzz around toilet paper discarded on the ground. A volunteer uses a shovel to remove waste that has pooled in front of a set of toilets.

The conditions show the health risks associated with the Remain in Mexico policy — which many have criticized for sending migrants to dangerous border towns — and how nonprofit groups are struggling to provide health care and other basic services without more support from the U.S. or Mexican governments.

Doctors Without Borders says that in three weeks in October, it did 178 consultations at the camp in Matamoros for conditions that included diarrhea, hypertension, diabetes, psychiatric conditions and asthma. More than half the patients were younger than 15.

Remain in Mexico has helped the U.S. government push down migration numbers at the southern border, a key priority of President Donald Trump. His administration said today that migrant apprehensions at the U.S.-Mexico border had fallen for a fifth straight month.

Mark Morgan, acting commissioner of U.S. Customs and Border Protection, credited Trump administration programs like Remain in Mexico, officially known as the Migrant Protection Protocols, saying they had “been a gamechanger.”

“MPP has absolutely been successful” from a law enforcement perspective, Morgan said.

When the U.S. and Mexico announced the program in December, Mexico agreed to provide work permits and other assistance to migrants forced to wait for U.S. court dates.

Last month, the U.S. Department of Homeland Security said it “understands” that migrants “are provided access to humanitarian care and assistance, food and housing, work permits and education.” The agency says the U.S. has provided more than $17 million in grants for shelters and other housing options.

But there is dire need in Matamoros, where more than 11,000 people had been sent back through Oct. 1, according to official numbers obtained by The Associated Press.

Many migrants receive medical care at a sidewalk clinic run by Global Response Management, a small nonprofit that works in combat and disaster zones. Asylum seekers help at the clinic, including two fluent English speakers who help translate — one from Cuba, the other from Venezuela.

Helen Perry, a nurse practitioner and Global Response Management’s operations director, saw a dozen patients one recent weekday as people lined up under a tarp shielding them from the sun.

A woman from southern Mexico says she had lingering neck pain from being attacked. A 3-year-old child from El Salvador had a fever and sore throat. A dehydrated 4-year-old drank Pedialyte as Perry examined his father’s toothache, using the light from her iPhone to look at the back of his mouth.

Perry then turned to a man from Cuba who was complaining of sharp pains in his chest that spread to his jaw and left elbow. She listened to his chest with a stethoscope, then used an ultrasound wand attached to her phone to observe the chambers of his heart. It appeared he was having a mild heart attack.

She sent the man off with volunteers to find a cab to take him to the hospital. A Red Cross ambulance arrived 15 minutes after he left. He was released from the hospital the next day.

“Speaking from having seen other humanitarian crises in the world, this is one of the worst situations that I’ve seen,” Perry said. “It is only going to get worse, and it is going to get worse rapidly.”

Justina and her baby, Samantha, are living it. Shortly after they entered the U.S. in September to seek asylum, they were taken to a Border Patrol station that migrants refer to as the “hielera,” or icebox.

Samantha got a fever and a cough. Eventually, she developed pneumonia.

Justina said agents took them to a hospital, where Samantha was treated and given antibiotics. When her health stabilized, they were returned to Mexico.

“They treated me very well inside there,” she said. “But when she came here, sincerely — when they deported me here — that’s when she got worse.”

Eventually, a few people in the camp helped the two take the bus to a Matamoros hospital, where the baby was again diagnosed with a respiratory infection. Samantha was hospitalized for about a week before being released with antibiotics again.

Their next court hearing is not until January.

“I don’t want anything to happen to my daughter,” Justina said last week as she held Samantha. “The truth is we face a lot of danger here.”

The camp is in Matamoros, a city of 450,000 people in the state of Tamaulipas, which faces endemic violence and corruption driven by cartels. The U.S. State Department warns Americans not to go to Tamaulipas, assigning the state the same warning level as Syria.

Morgan, the acting CBP commissioner, said widespread stories of migrants being kidnapped or attacked in Mexican border cities were “anecdotal.”

He also said that anyone who feared for their safety in Mexico could seek refuge at a U.S. port of entry. But many asylum seekers have been turned away at ports of entry or sent back to Mexico even after pleading to stay in the U.S. during their court hearings.

The Tamaulipas government runs its own clinic at the camp with the help of Doctors Without Borders. The camp now has shower stalls and a water pump, though many people still go to the river.

Officials in Matamoros and Brownsville are working with nonprofits to get flu vaccines, more medicine and new tents as winter approaches. Authorities also are watching for any signs of diseases like measles.

The Tamaulipas government has tried to move migrants to a new shelter it recently opened with room for several hundred people.

But migrants have largely refused to go. From the camp, they can see a tent courtroom built by the Trump administration on the U.S. side where they go to make their cases by video to judges.

Several people said they are afraid of missing out on their U.S. court dates or worry that Mexican authorities will try to deport them. Mexican officials have bused hundreds of migrants to cities far away from the border, with no offer of returning them for their hearings.

A widely shared video taken by a migrant shows a Mexican official appearing to imply that if families don’t leave the camp in Matamoros, authorities might take their children because of the hazards there — evoking the Trump administration’s family separations. Mexican officials later said families would not be separated.

Global Response Management plans to bring in a trailer soon to expand its capacity to treat migrants.

“The important thing is it’s not my job to fix the politics of it, it’s not my job to fix the immigration system,” Perry said. “My job is to go out there and give them medicine and give them mercy and give them hope.”

On the other side of the Rio Grande, there are signs that Remain in Mexico has worked as intended.

In the Rio Grande Valley, the southernmost point of Texas and for many years the busiest section for border crossings, the Border Patrol is apprehending around 300 people daily. That’s down from as many as 2,000 a day in May.

For years, large numbers of families would cross the Rio Grande by foot or in rafts. Smugglers would send families toward a few known areas and tell them to wait for Border Patrol agents to pick them up.

Now, routes near the river where agents would sometimes spot families several times a day are usually empty. The Border Patrol’s central processing center and its smaller stations are holding far fewer migrants.

Hundreds of agents pulled in to work at the processing center or monitor migrants are back to their regular duties.

“What we look forward to doing is our job and not what we were doing before,” one agent, Hermann Rivera, said during a recent tour.

Families requesting asylum now are detained quickly, then taken back to the border and released with future court dates, sometimes several hours away from where they originally crossed.

Agents are not supposed to send back children traveling alone and can exempt “vulnerable populations,” though there have been several cases of pregnant women and ill people returned to Mexico.

Rodolfo Karisch, the Border Patrol’s Rio Grande Valley chief, testified in a September court hearing that the agency was sending as many as 1,200 people back to Mexico from the region weekly.

“Who protects them, do you know?” asked Efrén Olivares, a lawyer for the Texas Civil Rights Project.

“I don’t know,” Karisch replied.