For many illegal immigrants who have managed to cross the Mexican border into the United States, the most deadly and dangerous part of their journey still lies ahead of them.

In southeast Texas, there is only one road leading into the U.S. interior, U.S. Highway 281, which stretches more than 1,800 miles from Mexico to Canada.

Though, just 80 miles from the U.S.-Mexico border is a Border Patrol checkpoint in Falfurrias, Texas. It's a last line of border defense that thousands and thousands of illegal immigrants risk -- and lose -- their lives trying to circumvent.

"So many people have died trying to get around the checkpoint they call this the corridor of death," narrated veteran correspondent Lara Logan in Fox Nation's "Lara Logan Has No Agenda."

"They succumb to the heat and the unforgiving terrain," she continued. "Most are never found. Their bones and bodies are scattered across Brooks County, where Sheriff Benny Martinez is in charge."

Martinez is 63 years old and he has lived in Falfurrias, which has a population of 7,300, all his life.

"It's a good small town that everyone is productive and they make the best of it," he told Logan as they drove through the small community.

"On our way through family neighborhoods, he pointed out homes used as stash houses for people, drugs and anything else the smugglers and cartels want to hide," said Logan in the Fox Nation documentary.

Falfurrias is 70 miles from the U.S.-Mexican border -- putting it squarely in the path of illegal immigrants attempting to enter the U.S.

"Why is this the place where people so often find bodies of illegal immigrants?" asked Logan.

"They're not prepared for the journey," replied Martinez. "They're being held in stash houses 'x' amount of days with not enough water, not enough food. During the summertime, we'll get up to 110, 115, the heat index. Even if it's midnight night... it's gonna be hot. So they're just not ready."

'UNBEARABLE' INTERVIEW OF WOMEN FORCED INTO SEX TRADE: LOGAN

He estimates that approximately 3,400 illegal immigrants have died trying to cross his county since 2009.

"There is no medical examiner, no morgue, and no more than one deputy on duty at a time," Logan reported. "When a body is found -- only one person to call. Sheriff Benny is responsible for recovering every one.

"What he does have at his office are records -- meticulously kept -- which he agreed to show us."

Martinez and one of his officers stacked binders, one on top of the other, on his desk. Each one contained information detailing the recovery of the human remains of suspected illegal immigrants in his jurisdiction.

In all, he has documented 673 deaths since 2009, but he estimated that there are five bodies that remain unfound for every one that he recovers.

"That means most of the bodies, you don't find," said Logan. "So this is like [a] graveyard?"

EXCLUSIVE: FOX NATION TEAM, DHS AGENTS EVADE MEXICAN POLICE AFTER THREATS WHILE FILMING

'Well, you can call it that I guess. You can use that term, because they're not going to be found," he conceded.

Logan pressed: "So you don't give up as time goes by?"

"No, we can't. We can't give up. That wouldn't be fair for them," said Sheriff Benny.

"Lara Logan Has No Agenda" is available exclusively on Fox Nation.

CLICK HERE TO SIGN UP FOR A FOX NATION FREE TRIAL

Fox Nation programs are viewable on-demand and from your mobile device app, but only for Fox Nation subscribers. Go to Fox Nation to start a free trial and watch the extensive library from Tomi Lahren, Pete Hegseth, Abby Hornacek, Laura Ingraham, Ainsley Earhardt, Greg Gutfeld, Judge Andrew Napolitano and many more of your favorite Fox News personalities.