At least one section of the southern border is seeing a massive spike in migrants crossing illegally into the U.S., with just weeks to go before the Biden administration will lose its ability to expel them under a frequently used Trump-era authority.

Fox News has learned from Customs and Border Protection (CBP) sources that in the El Paso Sector alone there were 1,926 migrant encounters in the span of 24 hours. That brings the total for the fiscal year, which began in October, to 105,263 for the sector.

That’s up 257% compared to this time last year, which itself was the highest number on record. 

Across the border there have been more than 400,000 migrant encounters by Border Patrol since Oct. 1, Fox has learned, and numbers are on track to surpass half a million before the middle of December, earlier than that number was reached in FY 2022 – which saw a record 2.3 million encounters overall.

BIDEN ADMINISTRATION'S BORDER WOES INCREASING, AS 2022 DRAWS TO A CLOSE 

Migrants Arizona

Migrants attempting to cross into the U.S. from Mexico are detained by Customs and Border Protection, Aug. 20, 2022, in San Luis, Arizona. (Nick Ut/Getty Images)

Official CBP numbers showed more than 230,000 migrant encounters in October, up dramatically from the more than 164,000 encountered in October 2021.

One Border Patrol agent told Fox that it had been a "rough" first quarter for agents.

"No support. No backup. No leadership," they said.

The increase in numbers comes as the end to the Title 42 public health order – which was implemented in March 2020 and has been used to rapidly expel a majority of migrants at the southern border – looms over the Biden administration’s border maneuvers.

A federal judge ruled earlier this month that the U.S. government’s use of the authority is unlawful and ordered a halt to Title 42 expulsions – before granting a five-week extension. It means the order will expire on Dec. 21.

While the Biden administration had attempted to end the order earlier this year (but was also blocked by a federal judge), it had recently expanded its use to include Venezuelan nationals.

REPUBLICANS, AHEAD OF HOUSE TAKEOVER, LOOK TO ZERO IN ON BIDEN ADMIN'S HANDLING OF BORDER CRISIS

The administration says it has a six-point plan in place that includes a surge in resources, greater tackling of smuggling organizations, more technology and a greater use of authorities like expedited removal and criminal prosecution for illegal border crossings.

But the end of the order has still led to concern from both Republicans and Democrats that it will lead to an additional surge in migrants trying to enter the U.S.

Moderate Democratic Sens. Kyrsten Sinema, D-Ariz., Mark Kelly, D-Ariz., Maggie Hassan, D-N.H., and Jon Tester, D-Mont., wrote to Homeland Security Secretary Alejandro Mayorkas this week expressing "deep concern" about the end of Title 42.

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"Record annual encounters have led to untenable situations. In Arizona, shelters have been forced well beyond capacity. This month, El Paso has seen over 700 migrants released directly onto city streets due to overcrowding," they said. "This is not safe, and creates a dangerous situation for migrants and communities."

But Mayorkas, who has previously described the border as "secure," has promised lawmakers that the agency has the situation under control.

"What we are doing is precisely what we announced we would do in April of this year, and we have indeed been executing on the plan," he said.