SAN DIEGO >> Over five years, the largest U.S. city on the Mexican border developed a well-oiled system to shelter asylum-seekers.

That system is being tested like never before as U.S. Customs and Border Protection releases migrants to the streets of California’s second-largest city because shelters are full. Since Sept. 13, about 13,000 have been dropped at transit stations with notices to appear in immigration court at their final destinations in the U.S., with about 500 more arriving daily.

Migrant aid groups blame a mix of circumstances for the shelter crunch: reduced government funding; CBP’s practice of sending migrants from Texas and Arizona to be processed in San Diego; and a surge in illegal crossings. Last week, President Joe Biden’s administration advanced plans for a border wall in Texas’ Rio Grande Valley and said it would resume deportation flights to Venezuela.

Before they are released in San Diego, some migrants being dropped off have been waiting between a double-layer border wall or camping under Border Patrol watch in remote mountains east of the city. CBP closed a major pedestrian border crossing from Tijuana, Mexico, on Sept. 14 and assigned more officials to processing migrants.

“Many do not know where they are, that this is San Diego, this is (the) San Diego region, the nearest airport is San Diego and how to get to their final destination. That is what we’re trying to provide support with,” said Paulina Reyes-Perrariz, managing attorney for Immigrant Defenders Law Center’s cross-border initiative.

Illegal crossings topped a daily average of more than 8,000 last month after a lull following the start of new asylum restrictions in May had diminishing impact and people from dozens of countries, notably Venezuela, were drawn by prospects of jobs and safety.

Similar to other U.S. border cities, about 95% of migrants in San Diego quickly move to other parts of the country. That’s a sharp contrast to cities far from the border, such as New York and Chicago. But the constant churn of exhausted, disoriented migrants from more than 100 countries has created other strains that the San Diego County government calls “an unprecedented humanitarian crisis.”

Last week, after a community recreation center could no longer handle the flow of migrants, the Border Patrol resumed drop-offs at a transit center. Arrivals from China, India, Brazil, Ecuador, Colombia and many west African countries filled a parking lot to charge phones, eat, use the bathroom and wait for free shuttle buses to the airport. “Is California far from here?” an Eritrean man asked volunteers.

Shuttles were announced in Spanish and Arabic. Al Otro Lado, a group aiding migrants, is seeking volunteers who speak Russian, Pashto, Creole, French, Portuguese, Amharic, Hindi, Mandarin, Somali, Turkish and Vietnamese.

“It’s a brief moment of intervention before they can move on to be connected with their loved ones,” said Kate Clark, senior director for immigrant services at Jewish Family Service of San Diego.

Shelters still accommodate families with young children, members of the LGBTQ+ community, the elderly and medically frail. The drop-offs are largely for single adults.

Since 2018, Jewish Family Service of San Diego and Catholic Charities together have helped more than 430,000 migrants in the region.

But Catholic Charities of San Diego recently halved capacity at the two hotels where it houses migrants to about 800 people, who stay an average of less than two days, said CEO Vino Pajanor. “The major issue” is less federal funding as San Diego competes with New York and other cities for support to aid migrants, he said.

Jewish Family Service has maintained shelter capacity at about 950 at a hotel and another large facility.

CBP did not respond to questions about the drop-offs. The Department of Homeland Security said last month that it has given $790 million for migrant shelters this year and asked Congress for an additional $600 million.

Aid groups say government support is needed even for the services at the San Diego transit center parking lot, where migrants get travel advice from volunteers over the steady noise of railroad crossing bells and bus horns. County supervisors voted today to spend $3 million to provide airport shuttles, internet connectivity, snacks and other basic services to migrants for three months.

The Border Patrol dropped off about 400 migrants by early afternoon one recent day as airport shuttles left about every hour. Overnight camping is prohibited. Migrants with flights within 24 hours are encouraged to wait at the airport.

The parking lot was a brief stop for Pedro Cardenas, 30, who was booked on a red-eye flight to Newark, New Jersey, after a grueling trip from Guayaquil, Ecuador. Smugglers squeezed about 14 migrants in a vehicle meant for five, forcing them to go hours without water or a bathroom break.

Cardenas, a mechanic on mining equipment, said violence and lack of work prompted him to leave his wife and child behind. He hopes to return with savings to buy land in Ecuador.

“I feel safer,” he said. “I feel happy but sad at the same time because I am not with my family.”

As night fell, volunteers at a church with room for 40 people sought to make sure no one would sleep on the streets. Rincon Marin, 26, arrived too late in the day for a flight to his final destination in Allentown, Pennsylvania, and accepted the church’s offer with a fellow Colombian who was headed to Columbus, Ohio.

“Happy, content,” Marin said to describe his feelings before rushing off to brush his teeth at a portable sink and squeeze into a car on his way to overnight lodging.