With windows tinted charcoal black and a hint of new-car smell lingering inside, the Chevy Suburban with California plates nearly made it through a border inspection booth. Then a customs officer spotted something behind the back seats.
Under the gray carpeting lay 14 undocumented Mexicans -- eight women, five men and a little boy -- packed together so tightly that some had to remove their shoes to fit.
They're part of a growing number of migrants sneaking across the border in cars and trucks. Some cram themselves into empty gas tanks, hollowed-out dashboards and even engines. Others hide inside cargo, from pinatas to washing machines.
Many try to ride across in plain sight of border agents, using falsified or borrowed documents. And while some smugglers use stolen cars or used vehicles that are hard to trace, others pay U.S. citizens to drive migrants across.
In fact, so many U.S. citizens try to drive carloads of undocumented migrants across that federal authorities have begun issuing $5,000 fines for Americans caught doing it. Nearly 300 fines have been levied since the program took effect Jan. 23, said Adele Fasano, Southern California director of field operations for Customs and Border Protection.
Now that National Guard troops are patrolling the border and Congress is discussing extending border fences, U.S. officials worry vehicle crossings could become even more common.
Most try to cross into California, where U.S. Customs and Border Protection officers captured 49,243 illegal migrants trying to drive into America last fiscal year -- 92 percent of all in-vehicle apprehensions nationwide. The rates this year were up slightly through April, even before troops began arriving at the border.
As illegal border crossings elsewhere become more risky, more migrants may try to drive across to San Diego, counting on Tijuana's sophisticated smuggling networks and a climate near the ocean that is relatively mild compared to the deserts further east.
"To put somebody in a compartment or a trunk out in Arizona or even Calixico (California) and the desert areas in Texas, the temperatures reach very high levels in the summer," Fasano said. "They could be looking at murder charges."
In the case of the Suburban, Mexican Alejandro Prieto tried to drive across using someone else's valid border-crossing card. He told prosecutors he's not a smuggler -- and that he only agreed to drive to avoid paying the $2,500 fee smugglers would have charged to sneak him into the U.S., according to court documents.
Prosecutors are pursuing smuggling charges against Prieto because he was carrying a child and such a large number of undocumented migrants. But the vast majority of drivers apprehended face no criminal penalty.
"The thing that causes us difficultly is just volume," said James Hynes, director of the busy San Ysidro crossing between Tijuana and San Diego. "We'd like to prosecute them all, but the system can't handle it, so we take the best cases."
Tens of thousands of migrants get away with it. Others barely escape alive.
Jesus Guerrero, 38, said he agreed to pay a people smuggler $2,600 to get him to Los Angeles, where a landscaping job was waiting.
Shortly after 7 a.m., he climbed into the trunk of a Toyota Camry with two women, fellow illegal migrants he had never met. A smuggler drove them into California through the Tecate border crossing, but failed to stop at a U.S. Border Patrol highway checkpoint.
As the car sped away, authorities punched holes in two tires, causing it to flip onto its side and collide with a concrete barrier. Rolling around in the trunk, Guerrero thought for an instant he had been killed.
"It's common, but it's very dangerous. I recommend nobody do it," said Guerrero, interviewed at a Tijuana migrants' shelter. "It's horrible."
Guerrero, who bruised his arm in the crash, said crossing had become too dangerous, and he planned to return to his native Sinaloa state, even though his wife and 10-year-old son -- an American -- live in Los Angeles.
Brigido Vargas, a 50-year-old mechanic from the western city of Guadalajara, said he would try to drive across after getting caught trying to hike through the Arizona desert.
"I don't even speak Spanish that well," Vargas said, describing his plans in English.
Vargas said his wife, four children and 12 grandchildren are all American citizens, but he's got a criminal history that bars him from becoming a citizen, even though he's lived in Los Angeles since age 9. He plans to drive over the border using his brother's California driver's license.
"In a car, you can get through the border really easily," he said.