U.S. border authorities encountered more immigrants in December 2023 than any month on record, blowing past alarming records set previously in the Biden administration.

More than 371,000 non-U.S. citizens were stopped when they attempted to enter the United States last month, including those who walked across without permission, lacked proper documents to pass through ports of entry, or were paroled in from abroad, according to U.S. Customs and Border Protection data released Friday evening. The previous record of 341,392 was set in August 2023.

The burgeoning border crisis will be a major obstacle for the Biden administration to address ahead of the November election, particularly given that voters nationwide have cited immigration as their top issue, according to new polling released this week. The record-breaking numbers also come on the eve of House GOP efforts to impeach Department of Homeland Security Secretary Alejandro Mayorkas for his handling of the border crisis.

“Secretary Mayorkas has outdone himself yet again — never have we seen such catastrophic numbers, even with historically high encounter numbers on his watch. December’s numbers serve as more undeniable proof that Secretary Mayorkas must be impeached,” House Homeland Security Chairman Mark Green (R-TN) said in a statement. “This is intentional, and it is a disaster.”

Green will introduce articles of impeachment against Mayorkas on Tuesday. He has not revealed the specific charges that he plans to charge Mayorkas with but held several hearings focused on how Mayorkas was derelict in his duties, though dereliction is not a high crime or misdemeanor.

The federal statistics revealed that 371,036 immigrants were encountered nationwide in December. Of that figure, Border Patrol agents arrested 251,222 for illegally entering the country nationwide, including 249,785 from Mexico, 1,178 coming in from Canada, and others apprehended on the coasts.

More than 119,000 immigrants were stopped at ports of entry for lacking proper documents to enter the country, including 50,000 who were released into the country through Biden-era initiatives that do not require immigrants to seek asylum.

The 50,000 figure was comprised of immigrants who entered through a year-old Biden administration initiative that allows immigrants outside the country to bypass the border and fly into the country through airports under the umbrella of temporary parole or request an appointment through the U.S. Customs and Border Protection’s CBP One phone app.

For the second option, immigrants in northern Mexico may apply for an appointment with a U.S. customs officer at a land port of entry with a customs officer, a move that the Biden administration rolled out to deter people from crossing illegally, but Republicans have criticized it as an excuse to parole into the country an unlimited number of people.

“Qualified beneficiaries who are outside the United States and lack U.S. entry documents may be considered, on a case-by-case basis, for advanced authorization to travel and a temporary period of parole for up to two years for urgent humanitarian reasons or significant public benefit,” the DHS website states. To apply, immigrants must have an adult sponsor in the U.S.

Since the government’s fiscal 2024 began in October 2023, the Biden administration has encountered more than 988,000 immigrants in those three months.

The number puts the United States on track to surpass the total encounters in fiscal 2023, when annual figures topped 2 million. The 2023 record surpassed all other years in CBP’s two-decade history. Numbers do not include illegal immigrants who were observed crossing and got away or those who went undetected while crossing illegally.

Of the nearly 250,000 Border Patrol arrests at the southern border in December, 102,000 people arrived as part of a family unit, 136,000 were single adults, and 12,000 were unaccompanied children.

Under the Biden administration, the number of arrests in any two given months has been as many people as were arrested in entire years over the past decade. Between 2010 and 2020, arrests in all but one year held between 300,000 and 500,000 per year. In 2019, agents arrested 850,000 in what was considered a crisis year, even by Democrats.

Migration throughout the Western Hemisphere surged as a result of economic instability brought on, in part, by the coronavirus pandemic. However, Republicans have blamed Biden‘s walking back a slew of Trump administration policies as sending a message beyond the borders that communicated it would not deport illegal immigrants.

Troy Miller, senior official performing the duties of CBP commissioner, did not explain the rise in the December figure in a statement issued Friday evening.

“The men and women of CBP continue to enforce our nation’s immigration laws at and between ports of entry and continue to work with our Mexican partners along our shared border. CBP remains vigilant to respond to the serious challenges we are experiencing across the southwest border,” Miller said.

The Biden administration has maintained that it is still in the midst of long-term efforts to rebuild the U.S. asylum and immigration system, but that progress takes time.

To deal with the surge in numbers, the Biden administration has focused its efforts on improving conditions within federal immigration facilities and quickly releasing people, which has angered Republicans since immigrants may remain in the country for years before appearing in court.

With funding from Congress, the Biden administration has opened numerous tent facilities across the southern border to detain the thousands of immigrants being encountered each day as they are processed and either removed from the country or released with a future immigration court date.

The government has not disclosed how many of the roughly 6 million encountered were released into the U.S., though Mayorkas divulged in a private meeting with DHS staff this month that 85% of immigrants were being let into the country.

The impact of immigrant releases on bus, airline, and other transportation networks since the influx at the border began in early 2021 prompted Gov. Greg Abbott (R-TX) to offer free bus rides to cities that immigrants would otherwise have had to pay to fly to.

He’s since taken control of borderland in Eagle Pass, Texas, and prevented access by federal border agents in what has created a legal firestorm between red states and the Biden administration.

The record-high illegal immigration has also put pressure on a bipartisan group of senators trying to hammer out a deal to improve border security in exchange for passage of a $110 billion supplemental funding bill to aid Ukraine, Israel, and Taiwan.