U.S. authorities reportedly detained a record 1.7 million-plus illegal migrants at the southern U.S. border in fiscal 2021.

The number was first reported Wednesday by The Washington Post, based on unpublished Customs and Border Patrol data. 

The CBP is expected to release the final fiscal 2021 data later this week. 

A flood of illegal migrants crossing the U.S.-Mexico border began soon after President Biden took office in January and remains high. The administration argued the early surge was consistent with historical seasonal trends. However, the report shows the high numbers continued through the sweltering summer months.

As Biden’s poll numbers fall, his handling of the crisis at the border remains his least popular issue. Along with the rest of the Democratic party’s field of presidential candidates, back in 2020 Biden promised to make the United States more welcoming to immigrants. 

Quickly after landing in the Oval Office, Biden stopped construction on the border wall and ended the “Remain in Mexico” policy that had limited illegal border crossings during the Trump administration. Biden also announced a 100-day pause on most deportations. 

Earlier this year, Biden assigned Vice President Kamala Harris to address the “root causes” of increased migration from the Northern Triangle nations – Guatemala, Honduras, and El Salvador. But the diplomatic mission appears to have resulted in no significant reductions, and Harris appears to have distance herself, at least publicly, from the issue. 

Mexican nationals were the single largest group of illegal immigrants into the U.S. in fiscal 2021, with the Border Patrol arresting more than 608,000. That figure places the administration in a challenging position as it relies on Mexico to be responsible for blocking caravan groups heading north toward the U.S. border.

The CBP categories the second-largest group as “other,” which includes Brazilians, Cubans, Ecuadorians, Haitians, Venezuelans and illegal migrants from dozens of other nations. The combined group accounted for 367,000 arrests. That figure was followed by the number of Hondurans who were arrested (309,000), and then Guatemalans (279,000), and then El Salvadorians (96,000.)