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Inside a drug smuggling tunnel on the US-Mexico border

8 December 2010 Last updated at 18:38 GMT

The US authorities have discovered 20 tonnes of marijuana, worth tens of millions of dollars, in one of the most advanced illegal tunnels ever found.

The passage is half a mile long and runs from inside a house in Mexico straight under the border with the United States and into a warehouse in San Diego.

The tunnel had its own lighting, ventilation and a system of tracks and trolleys for transporting drugs.

The BBC's Rajesh Mirchandani has been shown around.