One of the most sophisticated tunnels discovered in US history

American authorities discovered an unfinished 400m-long tunnel under the border with Mexico.

The pipeline, ventilation, and railway system were discovered in the tunnel. The tunnel was discovered by federal agents in co-operation with the US Migration Agency and customs administration Tuesday in the desert near San Luis in Arizona, the American Migration Agency announced.

The tunnel, which is 250 feet [1.2 m] high and about a foot [1 m] wide, also revealed the ventilation system, water pipes, power wires, and railway system, competent authorities announced.

The tunnel was discovered using underground training and cameras after a fountain was discovered near the border fence.

Authorities have discovered hundreds of tunnels at the US-Western border with Mexico in recent years. They claim the tunnels are used by drug cartels and criminal organisations to smuggle narcotics, people and weapons between the two countries.

Border control spokesman for the Yuma sector, Winni Dulaski, said the discovered tunnel is one of the most sophisticated in US history.

In January, American authorities discovered the longest smuggling tunnel, 1,300m, leading from the Mexican state of Baja California to US territory.

US President Donald Trump has pledged to build a wall on the border with Mexico in order to prevent illegal border crossings and drug smuggling, but critics note that tunnels are one of the ways such a barrier can be overcome.