Migrants rushed across the Mexico border Thursday, racing to enter the U.S. before pandemic-related asylum restrictions are lifted in a shift that threatens to put a historic strain on the nation’s beleaguered immigration system.

The imminent end of the rules known as Title 42 stirred fear among migrants that the changes would make it more difficult for them to stay in the U.S. And the Biden administration was dealt a potentially serious legal setback when a federal judge temporarily blocked its attempt to more quickly release migrants when Border Patrol holding stations are full.

With a late-night deadline looming, misinformation and confusion buffeted migrants as they paced the border at the Rio Grande, often unsure of where to go or what to do next.

he imminent end of the rules known as Title 42 stirred fear among migrants that the changes would make it more difficult for them to stay in the U.S. And the Biden administration was dealt a potentially serious legal setback when a federal judge temporarily blocked its attempt to more quickly release migrants when Border Patrol holding stations are full.

With a late-night deadline looming, misinformation and confusion buffeted migrants as they paced the border at the Rio Grande, often unsure of where to go or what to do next.

At Matamoros, across from Brownsville, Texas, throngs of migrants — some clutching small children — waded across spring river currents, pushed through thickets to confront a border fortified with razor wire. Other migrants settled into shelters in northern Mexico, determined to secure an asylum appointment that can take months to schedule online.

Many migrants were acutely aware of looming policy changes designed to stop illegal crossings and encourage asylum seekers to apply online and consider alternative destinations, including Canada or Spain.

“I don’t know what’s going to happen tomorrow,” said Jhoan Daniel Barrios, a former military police officer from Venezuela as he paced with two friends along the the border in Ciudad Juárez, across from El Paso, Texas, looking for a chance to seek refuge in the U.S.

“We don’t have any money left, we don’t have food, we don’t have a place to stay, the cartel is pursuing us,” said Barrios, whose wife was in U.S. custody. “What are we going to do, wait until they kill us?”

Last week, Barrios and his friends entered the U.S. and were expelled. They had little hope of a different result Thursday.

On the U.S. side of the river, many surrendered immediately to authorities and hoped to be released while pursuing their cases in backlogged immigration courts, which takes years.

It was not clear how many migrants were on the move or how long the surge might last. By Thursday evening, the flow seemed to be slowing in some locations, but it was not clear why, or whether crossings would increase again after the coronavirus-related restrictions expire.