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.