One sector of the southern border has seen more than 100,000 illegal encounters since Oct. 1, which is a 163% increase from the same time period in 2020.

The numbers come as the U.S. has struggled to cope with an influx of migrants and the Biden administration moved to reestablish his predecessor's "Remain in Mexico" policy. A source from the Homeland Security Department told Fox News that the Rio Grande Valley (RGV) sector recently saw 2,284 illegal encounters within 24 hours. Similar numbers emerged in November, with at least 262 migrants making it past overwhelmed agents in that sector.

RIO GRANDE VALLEY BORDER PATROL ENCOUNTER NEARLY 2,000 MIGRANTS IN 24 HOURS, HUNDREDS GET PAST AGENTS

Overall, illegal encounters have reached 101,808 since Oct. 1 with more than 9,500 getaways. 

Last week, the Biden administration said it would reinstate Trump's controversial migrant protection protocols (MPP), also known as the "Remain in Mexico" policy, which keeps migrants on the other side of the border while they await hearings.

DHS Secretary Alejandro Mayorkas issued a memo to formally end the program in October, and DHS emphasized on Thursday that he "repeatedly stated that MPP has endemic flaws, imposed unjustifiable human costs, pulled resources and personnel away from other priority efforts, and failed to address the root causes of irregular migration." 

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Last week, DHS said it would start the reimplementation on Monday. "DHS will begin the court-mandated reimplementation in one location on December 6, and quickly expanding across the Southwest Border based on discussions with the GOM to address security concerns and operational constraints," a press release reads.

Republicans have blamed the ongoing border surge on the Biden administration's policies, including revoking MPP, while the administration has criticized its predecessor for shutting off legal asylum pathways.

Fox News' Adam Shaw contributed to this report.