December saw the most families caught at the U.S.-Mexico border ever, with nearly 32,000 family members apprehended.

According to Department of Homeland Security data released Wednesday, 31,901 of the 60,782 migrants from Central America who were apprehended by Border Patrol agents stationed at the U.S.-Mexico border or turned away by Customs and Border Protection officers at official crossing points were families.

That is the highest number of families to ever attempt migrating, both legally and illegally, into the U.S. in one month, according to federal data.

Nearly 90 percent of all families – 27,518 – entered in rural or suburban areas between dozens of ports of entry on the southern border.

It's the third month the number of family members exceeded the number of single adults, which was under 24,000.

50,753 people were arrested for trespassing from Mexico in December. It marks the third month in a row that more than 50,000 people have illegally crossed into to the U.S. Another 10,000 people who tried to enter through ports were told they lacked the documents to do so.

Illegal immigration apprehensions at the southern border have skyrocketed since Trump's first few months in office, when 15,000 to 20,000 people were reported being apprehended per month.

One of the reasons for the increase is the change in demographics of those entering. Caravans of people fleeing violence, unemployment, and crime in El Salvador, Guatemala, and Honduras have allowed families to migrate north without having to pay the average $8,000 fee for smugglers to get them through Mexico.

Since early fall, Border Patrol has seen Mexican smugglers lead groups of 100 to 300 people over the border. Historically, groups of five to 10 people would be escorted over the border by a smuggler.

The dramatic increase in group size and their arrival in rural parts of Arizona and New Mexico has presented a major challenge for Border Patrol, which is responsible for arresting people who have illegally entered.

In December, two young children traveling from Guatemala died after having entered New Mexico as members of large groups. The deaths marked the first in a decade, prompting Democrats to launch investigations into the incidents.

During the last week of December, CBP began referring hundreds of migrants taken into custody in these rural parts of the southe rn border to medical professionals. More than 450 migrants were referred to medical professionals for care over a nine-day period.