There are three migrant caravans headed to the United States’ southern border with Mexico, according to top Pentagon official John Rood.

Rood testified to the House Armed Services Committee on Tuesday that one of the caravans contains over 12,000 migrants.

“Current information shows that a caravan of over 12,000 people — there’s three that we are tracking, that the DHS is tracking en route, one that is over 12,000 by the latest estimate,” said Rood, who is the under secretary of Defense for policy.

Rood said there are currently more than 2,300 active duty troops at the southern border, down from a high of 5,900 in November.

But defense officials say several thousands more active duty troops are expected to head to the border in the coming weeks, to assist the Department of Homeland Security with laying down more concertina wire, and helping to monitor the border between points of entry.

Democrats, who now control the House, called Pentagon officials in to testify on President Trump’s order of active duty troops to the border in October, which they have called a political stunt by the White House before midterm election.

But defense officials testified that it was the Pentagon — not the White House — decided that active duty troops were able to deploy faster and were better resourced to deal with the caravans headed to the border than National Guard and reserve forces.

“That was a decision made inside the Department,” said Navy Adm. Michael Gilday, the director for operations of the Joint Chiefs of Staff.

Democrat lawmakers also questioned whether there was a crisis that necessitated the deployment of troops, when the number of illegal immigrants coming across the border have been higher in previous years.

“The difference is really the caravans and really the nature of the asylum seekers,” Rood said.

Ranking Member Mac Thornberry (R-TX) agreed. “One of the things that changed is that now we have thousands, and tens of thousands of migrants who are coming in caravans which we have not seen before,” he said.

“The days when we had a greater number of people — but most of them were from Mexico, and you could simply put them back across the border — are very different from these large family groups, 10, 12,000 people coming. So yes, it changed the requirements,” he added.

“We have 42 percent increase in the number of family units. We have 60,000 unaccompanied children that were caught last year,” Rep. Vicky Hartzler (R-MO) added. “I’m a former teacher and a mom, this is a humanitarian crisis.”

Rep. Mike Rogers (R-AL) noted that administrations have been sending active duty troops to the U.S. border with Mexico “since Alamo.”

“I’m just astounded by the fact that we continue to act stupid in Congress and fuss over things like $5.7 billion in fencing, and it cost us $11 billion dollars to shut the government down,” he said.

According to Rood, the projected costs for the active duty deployments by the end of January is $132 million. He said the costs for the National Guard deployment for 2018 and 2019 to amount to $550 million.

But Rood said that even with the troop deployments, illegal immigrants were still coming across the border.

“Just in the last three months alone, CBP reports apprehending 145,000 illegal immigrants,” Rood said.

He said last year, there were more than 521,000 apprehensions by law enforcement, with a larger amount of people not apprehended. He said that was up from 415,000 the year before.

“In the last two years alone, a larger number than the population of Washington, D.C. have been apprehended, or a city the size of San Francisco, apprehensions in two years,” he said.

Reps. Hartzler and Mo Brooks (R-AL) noted that there is existing authority the administration could use to have the military build a border barrier without declaring a national emergency, through Section 284 of Title 10 of the United States Code.

“Congress has actually given the DOD the ability to provide military support to law enforcement agencies specifically for countering the counter-drug purposes. Section 284 of Title 10 of the United States Code authorizes the DOD to provide support to counter drug activities to control the transnational organized crime,” Hartzler said.

“The law clearly identifies various activities that DOD is authorized to conduct including the construction of road and construction of fences, light installation along smuggling corridors, aerial, ground reconnaissance and transportation,” she added.

Rood responded that Hartzler was correct.

“As you correctly point out, Section 284 of Title 10 does provide the secretary of defense the authority in performance of that counter drug mission such as blocking drug smuggling corridors to erect barriers, fencing, provide road construction things of that nature to aid in that counternarcotics mission,” he said.

“We have already given the authority to do this and we have a very critical mission to keep people safe and make sure that people don’t die as a result of these transnational drug cartel activity and currently they are,” Hartzler addded. “So it’s imperative for us to find a solution.”

Brooks also pressed Rood on whether the Pentagon would carry out an order by Trump to build necessary barriers under Section 284 without declaring a national emergency.

“If we judge it to be a lawful order, yes sir, and I assume it would be,” Rood said.