The Mexican cartels' tunnels under the U.S. border keep getting better and better—at least for the cartels. This week saw three of them discovered, with sharply increasing degrees of sophistication, including a rail line and ventilation system in an unfinished project discovered Thursday. And here we were impressed by the wagons and electricity in one tunnel found last Saturday. Less than a week later, there's a tunnel that makes it look like a kid's pillow fort by comparison.

As The Associated Press' Elliot Spagat and Jacques Billeaud report, the latest two tunnels "were incomplete, including one that the Mexican army found in a Tijuana warehouse Thursday with more than 40 tons of marijuana at the entry. The passage extended nearly 400 yards, including more than 100 yards into the United States." Yep, you'd sure want a railcar system to transport 40 tons of weed. 

Obviously the concern here is that there could be a lot more tunnels, capable of transporting even more stuff (drugs, guns, people, whatever), that we don't know about. But reading these reports, we're as fascinated as we are concerned, just to find out what the next advance in Cartel tunnel technology might be.