(CNN Spanish) - A tunnel that crossed the border between the United States and Mexico was discovered in the Sonoran desert and has been called by the US authorities as the "most sophisticated in history."
The structure, which had not been completed, entered more than 396 meters into Mexican territory from the border and connected San Luis, Arizona, with San Luis, Sonora, the Office of Homeland Security Investigations reported in a statement Thursday.
The one meter wide and 1.2 meter high tunnel was discovered in mid-July. It was equipped with a ventilation system, electricity, water pipes and even a rail system, the United States Government reported.
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"This appears to be the most sophisticated tunnel in US history and certainly the most sophisticated I have ever seen in my career," Acting Border Patrol Chief Carl Landrum said in the statement.
The Office of National Security Investigations said that, upon completion, the tunnel would be used for illegal trafficking activities between the two countries.
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