U.S. Border Patrol agents and Homeland Security Investigations uncovered a man-made tunnel entering the United States from Mexico on Thursday. Agents discovered it in El Paso, Texas, near a storm drain system by the border wall during a security sweep of the area.

It is suspected that the “sophisticated cross-border tunnel” was used for human trafficking and drug smuggling in and out of the U.S. The tunnel’s dimensions were 6 feet tall and 4 feet wide. It had a lighting and ventilation system and was supported with wooden beam braces, according to U.S. Customs and Border Protection.