Border Patrol agents took 31 undocumented immigrants into custody after completing a search of a belly dump trailer.

The search occurred on Sept. 23 when a tractor hauling a belly dump trailer approached the checkpoint on Highway 83 in Laredo, TX.

A canine alerted the presence of concealed humans, and 31 illegal immigrants were found inside.

After the discovery, the Webb County Fire Department assisted agents by supplying the individuals a manner to climb down from the height of the trailer.  

The individuals were determined to be illegally present in the United States from the countries of Mexico and Guatemala.

The driver, a U.S. citizen, was arrested and is pending further investigation. The rest of the individuals were taken into custody.

Homeland Security Investigations took over the investigation.

Border Patrol seized the tractor and trailer.