U.S. authorities intercepted 180,034 migrants along the Mexico border in May, and a growing share have been arriving from nations outside Central America and Mexico, according to U.S. Customs and Border Protection data published Wednesday showing illegal crossing at a new 20-year high.

Border arrests have soared since President Biden took office, and the CBP figures show May was the busiest month yet. While the administration was overwhelmed this spring by a record influx of migrant teenagers and children crossing without parents, their numbers continued to decline last month, as did family groups, the data shows.

Those declines were offset by another increase in single adult migrants, with 121,082 apprehended last month. U.S. authorities have used a provision of the public health code to promptly “expel” the majority of those adults to Mexico, but the circular pattern has allowed many to attempt entries again and again without fear of legal consequence or jail time.

CBP officials said the 180,034 taken into custody in May was not a tally of unique individuals, and 38 percent of those it detained had been stopped along the border during the previous 12 months.

“The large number of expulsions during the pandemic has contributed to a larger-than-usual number of noncitizens making multiple border crossing attempts, and means total encounters somewhat overstate the number of unique individuals arriving at the border,” the agency said in a statement.

CBP officials did not take questions from reporters on the latest enforcement data, publishing the figures in a short news release.

The Biden administration published the May enforcement data a day after Vice President Harris concluded a trip to Guatemala and Mexico, where she met with the presidents of both nations to discuss strategies to reduce illegal migration.

The latest CBP data show a major increase in the number of non-Mexican and non-Central American migrants encountered along the border, however. CBP detained 40,067 migrants from other nations last month, up from 9,671 in January, according to the latest figures. Those migrants included large numbers of Cubans, Haitians, Ecuadorans, Brazilians and citizens of African nations, officials said.

During her visit to Guatemala, Harris issued a stern warning to would-be migrants considering an unlawful trip to the United States. “Do not come,” she said. “Do not come.” Her comments drew criticism from some Democrats who considered the warning too harsh, while GOP lawmakers faulted her for not visiting the U.S. southern border.

The Biden administration reported more progress last month in its efforts to quickly transfer unaccompanied minors from Border Patrol custody to Department of Health and Human Services shelters. Teens and children spent an average of 26 hours in CBP custody in May, down from an average of 92 hours in April, the agency said.

“This sustained progress is a result of the steps [the Department of Homeland Security] took to reengineer processes and mobilize personnel Department-wide, including designating FEMA to lead a whole of government effort to assist the Department of Health and Human Services (HHS) with establishing temporary facilities that provide a safe, sanitary, and secure environment for unaccompanied children,” the CBP statement said.

More than 350 officers from U.S. Citizenship and Immigration Services have been assigned to run background and screening checks on family members and other sponsors seeking to take custody of the minors from HHS.

Last month, 14,158 teens and children arrived without parents, down from 17,148 in April. U.S. officials say the deployment of thousands of soldiers and police by the Mexican government along migration routes is the biggest reason for lower numbers of children and families reaching the U.S. border.