When border officials find drug tunnels that lead to the U.S., they are filled with cement and sealed off.
But that doesn’t necessarily seal off their future use.
According to a report by the Los Angeles Times, the tunnels aren’t completely closed off across the border in Mexico. While the entry is sealed, the rest of the tunnel is left alone.
Over the last decade, U.S. Customs and Border Protection has spent roughly $9 million to block off the entry points of illegal tunnels.
The Mexican government says it lacks to funds to do the same. This allows drug cartels to dig up a new path within the tunnel and re-direct a passageway to the U.S.
Since some of these sophisticated tunnels have lighting, ventilation and even a rail system, it makes them even more attractive for drug cartels because the infrastructure is mostly installed.
“Until 2007, the U.S. didn't fill in the tunnels either,” said Ev Meade, director of the University of San Diego’s Trans-Border Institute. “We just capped the entry points and left them alone, and Mexico basically did the same."
Back in November 2010, an underground tunnel that led to a warehouse in Otay Mesa was discovered by border officials. The 600-yard tunnel ran from Mexico to the U.S.
It was filled up on the U.S. side, but in 2014 authorities discovered that drug traffickers had dug up a new path from inside.
“There’s so much talk about the border wall," Meade said. “It misses all the other ways in which people and goods get into the U.S. without permission. The tunnels are one of them, there’s also airports and sea port entries.”
Complicating things even further is the political tension between the U.S. and Mexico.
President-elect Donald Trump has promised to build a wall along our southern border to stop illegal immigration and drug trafficking. But tons of drugs have been trafficked into the U.S. through border tunnels.
"We spend $18 to $20 billion a year,” Meade said. “That’s more than all the rest of federal law enforcement combined. That’s excluding the money we spend on the drug war in Mexico. Depending on how you count it, it’s another billion dollars or so a year. Through collaboration, they’ve been able to arrest the heads of the most important drug cartels in Mexico — the problem is that hasn't done much to go after the underlying business.”