The Federal Bureau of Investigation worries that corrupt U.S. officials at the nation's border crossings are exposing Americans to serious risk, and are stepping up efforts to root those officials out.
With evidence of corrupt U.S. border officials allowing illegal immigrants to enter the country in exchange for bribes, the FBI is concerned terrorists or materials that could be used in a terrorist attack might also slip through.
"If you're a corrupt border official, and you're allowing illegal immigrants to come into the country, you're not going to know who you're letting in," Kevin L. Perkins, assistant director of the Criminal Investigative Division for the FBI, told ABC News.
In one instance at the U.S.-Mexico border, FBI video surveillance obtained by ABC News caught a truck full of illegal immigrants pulling up to Customs and Border Protection officer Michael Gilliland, and being waved through his border inspection lane for $100,000, officials said.
And in Texas, an undercover FBI operation allegedly caught a deputy sheriff in the act.
"You can either pay me here or follow me all the way to Petula and you can pay the judge," the deputy sheriff told an undercover FBI agent posing as a Mexican national, despite the agent having broken traffic laws.
"So the fine is $150 here," the deputy sheriff was recorded as saying.
"You don't have to worry about court or anything," he said, after the undercover agent handed over $150 in cash.
"I don't worry about nothing?" the agent asked.
"No," the deputy sheriff replied.
The FBI says corrupt border officials willing to betray their badge for a price represent a potentially grave national security threat.
"Whether it's a truckload of illegal narcotics or whether it's components of a weapon of mass destruction. We have to know what those are. We have to have assurance that our borders are safe, that our borders are secure and that we can find these things before they enter our country," said Perkins.
Custom and Border Protection is one of the key agencies under increasing federal scrutiny. They are the frontline sentries in the fight against illegal immigration. Right now, the bureau says they are investigating more than 100 such cases of corruption.
"They are the first line of defense coming into the country. They are the people that check people, goods and other things coming across the border," said Perkins.
Since 2004, 94 federal customs officials have been charged with mission-related corruption. The agency said it's taking the problem seriously and has been agressively expanding efforts to root out crooked employees.
The case of customs officer Margarita Crispin underscores the seriousness of the problem.
Crispin was recruited by a powerful Mexican cartel. She was sent to the agency as a mole, to help smuggle tons of drugs through border checkpoints in El Paso, Texas. For her trouble, the cartel paid Crispin $5 million. She was arrested in July 2007, and in April 2008, pleaded guilty and was sentenced to 240 months in prison.
Lloyd Easterling, acting public affairs director for the CBP, said the federal government has ramped up its efforts to root out corrupt border officials.