Homeland Secretary Jeh Johnson testifies on Capitol Hill in Washington, Tuesday, Sept. 27, 2016, before the Senate Homeland Security and Governmental Affairs Committee hearing on on terror threats. (AP Photo/Pablo Martinez Monsivais)

(CNSNews.com) - Poverty and violence in Central America continue to push hundreds of thousands of illegal aliens toward the United States, Homeland Security Secretary Jeh Johnson told Congress on Tuesday. He said he's particularly concerned about infiltrators from the Middle East.

"I am concerned about what we refer to as the special interest alien that comes from the other hemisphere that turns up on our southern border," Johnson told the Senate Homeland Security Committee.

"We don't see this very often. It's a very small percentage of those who are apprehended on our southern border who are coming from the Middle East region. We now have in place systems to almost immediately investigate that person when we apprehend them.

"I have put in place a working group within my department over the last several months to work with the law enforcement components of other governments in Central and South America to interdict these people before they get to our border and to share intelligence about what we are seeing.

"The smuggling organizations that focus on migrants from the Middle East are a relatively limited number. And so what we're doing, and what I want to do more of, is focus our law enforcement efforts on cooperating with the law enforcement agencies of Central and South American governments to break these organizations up.

"You began your question by referring to migrants from the other hemisphere, and I think that that's a very legitimate concern and we're focused on it," Johnson told Committee Chair Sen. Ron Johnson (R-Wis.).

Johnson also gave Congress some numbers: In Fiscal Year 2014, the total number of people crossing from Mexico into the United States was around 479,000; that number dropped to around 331,000 in Fiscal 2015.

"My projection for F.Y. '16 is that we'll come in at around 407,000, 408,000 apprehended on the southern border. That's a fraction of what it used to be, but it's still too high," Johnson said.

Secretary Johnson said the government has "gotten better" at processing unaccompanied alien children.

Sen. Ron Johnson noted that in Fiscal Year 2014, 68,000 unaccompanied children crossed the border. "So far in 2016, we're up to 54,000. In terms of family units back in 2014, there were about 68,000 family units. We're already at 68,000 with a month to go," the senator said.

"So we've certainly gotten more efficient at processing and dispersing -- apprehending, processing and dispersing. Let's face it, a lot of them just turn themselves in.

"My concern is, because we have not stopped the flow or reduced the flow -- because we still have enormous incentives for people to come into this country, we haven't succeeded in doing that, I'm concerned about the diversion of resources on the border, having to take care of what remains I think a humanitarian crisis."