Since the beginning of May, Border Patrol agents have uncovered more than 40 human-smuggling attempts in which more than 400 illegal immigrants were found inside tractor-trailers.

Exactly 406 people were taken into custody by federal law enforcement in 42 such incidents documented on the U.S. side of the southwest border from the beginning of May through early July.

Last weekend, 64 illegal immigrants were arrested in five such incidents, according to U.S. Customs and Border Protection.

A CBP spokesperson could not confirm if the number of tractor-trailer trafficking attempts was higher than in previous years.

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The smuggling attempts are also classified by Border Patrol as rescues because of the conditions inside the trucks that have led to hospitalizations and even the deaths of those inside.

As of Thursday, the Border Patrol stated it had rescued 2,809 people since Oct. 1, 2017, which marked the beginning of fiscal year 2018.

“In addition to securing and protecting our nation's borders, frontline Border Patrol agents are committed to reducing heat-related injuries and preventing deaths along our borders," U.S. Border Patrol Acting Chief Carla L. Provost said in a statement. “These rescues are a result of stepped-up enforcement at our immigration checkpoints coupled with our search and rescue efforts that are key to preventing unnecessary loss of life.”

CBP said the agency was directing more resources and personnel toward southern Arizona in light of temperatures that are expected to hit 115 degrees this week.

In April, a Louisville, Ky., man was sentenced to life in federal prison for transporting dozens of illegal immigrants in a scorching hot tractor-trailer. Ten people were found dead inside the truck last July. The case made national news, and similar truck-smuggling incidents have been documented in the year since then.