More than 75 drug-smuggling tunnels have been discovered under the U.S.-Mexico border in just the past six years, and one of the more intriguing cases involves 17 Mexican men who claim they were kidnapped and forced to carry out the work for months before Mexican authorities found them.
There's always been some mystery surrounding tunnels. Diggers were thought to be well-paid cartel loyalists or, as urban legend goes, laborers killed soon after the tunnel's completion to ensure its secrecy.
I met one of those 17 men who say they were kidnapped and forced to dig a tunnel last year. He says he was enslaved 35 feet below the border for months and lived to tell his side of the story from a Tijuana prison.
He was at Tijuana's infamous La Mesa, one of the most overcrowded prisons in Mexico. Built for 2,600 prisoners, it now houses more than 7,000.
He and 16 other men have been there for a year, after being caught digging the underground tunnel.
I waited for him in a small room next to the warden's office. Earlier, the warden warned me not to ask too many probing questions. This is a delicate case, he said. It touches a lot of powerful people in the city.
The tunnels burrowing under Tijuana are thought to be built by Mexico's most powerful drug organization, the Sinaloa cartel. The group, led by Joaquin "El Chapo" Guzman, is one of the few with the expertise and money on average about $2 million needed to build one of the underground wonders.
After about 10 minutes, the guards escorted in a short man, dressed in the prison's standard gray sweatpants and T-shirt. His hair was closely cropped. His accent was thick, like most rural farmers from Mexico's northern states. He asked me if he's in any danger if he tells me his story. I told him I really didn't know; only he could weigh that risk. But I promised not to use his name.
He started telling me his story. It began back in the winter of 2012, just four miles from this prison, in Tijuana's Mesa de Otay neighborhood.
High on a bluff hugging the international border and the huge commercial crossing into San Diego, Mesa de Otay bustles with activity. Eighteen-wheelers barrel down the wide streets, packed with everything from TVs to small medical devices assembled in Tijuana's foreign-owned factories. Warehouses line the dusty boulevards some have signs; others don't even have a street number on their door fronts.
The warehouse where the tunnel digger was found is about a quarter of a mile from the border. He says he was brought to it in November 2012. The warehouse is abandoned now, and it still has crime-scene tape and a padlock on the front door. With all the truck traffic here, you could imagine how loud noises coming from inside the building, or deep underground, would be masked.
The tunnel digger said he was tricked into going there. He was working day jobs in a border town until he had a fight with his wife. He picked up and left and decided to head north to San Diego for a while, to cool off and make some money. He had made the illegal trip many times before. He rented a room in a rough neighborhood in Tijuana known as a reliable place to find a smuggler.
"I was drinking a soda at this little store in front of the room I was renting, and this guy, who I had talked with a few times before, drives by," the tunnel digger said in Spanish.
The other man said he had found a smuggler. He said he could show the tunnel digger the safe house so he would know where to go.
The tunnel digger climbed in the vehicle. But he said the man identified in court documents only as Carlillos took him to a warehouse, not a home.
"Someone rolled up the huge metal door and we drove in. A pickup truck pulled in behind us, and then I heard the door come down," he said.
He said six men with ski masks and rifles jumped out of the truck.
"They threw me to the ground and started beating me up, threatening me. I wanted to run, but there was nowhere to go," he said. "They told me what I was going to do, and if I didn't, they would kill me."
San Diego Warehouses: The Exit Door
Just over the border fence in San Diego sit hundreds of warehouses. Federal officials have found the exit doors for Tijuana's tunnels tucked into back offices and even in bathrooms.
Joe Garcia is a federal agent on San Diego's Tunnel Task Force. His group has discovered some of the biggest underground passageways in the region, including last year's so-called supertunnel, which stretched 600 yards. Eight-and-a-half tons of marijuana and more than 300 pounds of cocaine were stuffed inside. Garcia says the tunnels are sophisticated and quite a feat to dig without heavy machinery, which is too noisy and too big for the narrow passageways.
"It's good old-fashioned, hard, manual labor," he said. "These guys are filling buckets or sandbags of earth and are moving them either completely out or putting them somewhere else in the tunnel. It is hard, hard work."
The tunnel digger said they worked in 12-hour shifts, from 6 to 6. He said he worked the night shift with six others.
"There was this red laser beam we had to follow, right down the middle," he said. "If we went crooked or off a bit, the men with the ski masks would come down and beat us. We had to dig 3 meters every day. If we didn't, they told us we were lazy and beat us."
The digger said he never saw anyone's face except Carlillos' and that of the man who brought them food. Some days the man with the food didn't come.
After two months, they had dug about 200 yards, and it was getting harder to breathe in the tunnel. The men in the ski masks brought in tubing and pumped in oxygen.
It was nearly February. At that rate, the tunnel would reach a San Diego warehouse in plenty of time before Baja, California's marijuana harvest was ready to pick.
Jose Mario Vega Hernandez of Mexico's defense department said an anonymous tip led authorities to the tunnel on Feb. 4, 2013.
The tunnel digger said he was so happy to see them. The men rushed to thank the soldiers and said they were being held against their will.
He said the soldiers told them to be quiet and forced them to the ground. They were arrested and taken to prison.
The 17 men were given one public defender. In their declarations, obtained by NPR, their stories are the same: The man known as Carlillos promised them either work or help to get across the border illegally.
In the year they've been in jail, several of the men I've spoken to say they've rarely seen their attorney, who refused to speak with NPR. His supervisor declined to be recorded, but said it is a complicated case and that the lawyer is giving the best defense possible. She added, though, that his caseload numbers in the hundreds.
Like the warden of the prison, Jose Mario Vega Hernandez of Mexico's defense department said he has heard others accused of drug crimes claim kidnapping. He said the men have a lot of evidence against them 10 kilos of marijuana were found at the warehouse and face up to 35 years in prison.
The tunnel digger said he never saw marijuana in the warehouse, except on the day the army arrived.
His family members, who live hundreds of miles away, said they feel helpless. They have little money and can't visit or hire a private attorney. But they said they are glad he's alive.
The tunnel digger said in all those months underground, he was convinced the men in the ski masks were going to kill him once the passageway was complete.
In a business as risky as this, witnesses are a liability.
Now he says he thinks about how he might be in this prison for the rest of his life. He's glad to be alive, but says it's not fair and it's just not right.