WASHINGTON (AP) — A surge in Cuban and Nicaraguan arrivals at the U.S. border with Mexico in December led to the highest number of illegal border crossings recorded during any month of Joe Biden’s presidency, authorities said Friday.

The extraordinary influx came shortly before Biden introduced measures on Jan. 5 to deter Cubans, Haitians, Nicaraguans and Venezuelans.

U.S. authorities stopped migrants 251,487 times along the Mexican border in December, up 7% from 234,896 times in November and up 40% from 179,253 times in December 2021, Customs and Border Protection said.

Cubans were stopped nearly 43,000 times in December, up 23% from November and more than quintuple the same period a year earlier. Nicaraguans were stopped more than 35,000 times, up 3% from November and more than double from December 2021.

More migrants were also stopped from Ecuador and Peru.

The influx from Cuba and Nicaragua made El Paso, Texas, the busiest of the Border Patrol’s nine sectors on the Mexican border for a third month in a row. The city was overwhelmed with migrants who were released to pursue their immigration cases in the U.S. in the weeks leading up to Biden’s visit on Jan. 8, his first to the border as president.

The number of Venezuelan arrivals remained far below September highs, when the South American country was the second-highest nationality at the border after Mexicans. In October, the U.S. agreed to accept up to 24,000 Venezuelans on humanitarian parole, while Mexico agreed to take back the same number who entered the U.S. illegally and could be expelled under a pandemic-era rule to deny rights to seek asylum on grounds of preventing the spread of COVID-19.

Biden said this month that the U.S. would admit up to 30,000 people a month under humanitarian parole from Cuba, Haiti, Nicaragua and Venezuela, allowing them to live and work for two years if they apply online, pay airfare and find a financial sponsor. At the same time, Mexico agreed to take back the same number from those four countries who enter the U.S. illegally and can be removed under the pandemic-era rule known as Title 42.

Troy Miller, CBP’s acting commissioner, signaled that the latest measures may be having the desired effect.

“Early data suggests the expanded measures for Cubans, Haitians, and Nicaraguans are having a similar impact, and we look forward to sharing the additional data in the next update,” he said in a news release.