(NewsNation) — The effort by Texas state troopers to find migrant “stash houses” has produced big numbers in three years: nearly 500 homes containing about 5,000 people discovered. But the effort is far from over.

“The ‘gotaways,’ the gangs that were … going to exploit the situation on the border,” remain a huge concern, said Lt. Chris Oliverez of the Texas Dept. of Public Safety.

Unlike most migrants who immediately turn themselves to Border Patrol agents to begin the legal immigration process, “gotaways” will join many others in a “surge” of a border crossing, then escape in the chaos.

“They’re caught on a camera and Border Patrol didn’t have the resources to apprehend them, or they weren’t even caught on a camera at all,” Oliverez told “NewsNation Prime.”

And that’s where the stash houses come into play.

Drug cartels and gangs have taken over motels, buildings and homes in the middle of otherwise peaceful neighborhoods. People who evade Border Patrol capture will stay for a few days or weeks until they move on to other places in the U.S.

Immigration law aside, Oliverez says there are dangerous people in those stash houses.

“It’s not just economic migrants … but also gangs, criminal gangs. Special interest aliens that have ties to “special interest” countries that have ties to terrorism, he said.

“We do have women and children that are in these stash houses. They’re being kept, either because they need to provide payment or they’re trying to get ‘em further moved into the interior.”

But those who perhaps can’t pay up find themselves the victims of sexual assault and abuse, he said.

Texas troopers recently raised a stash house in Webb County and found 29 people inside – migrants from Mexico and Honduras.

“Operation Lone Star” has been offering people rewards of up to $5,000, and the promise of anonymity, for information on stash houses.