Salvadorean migrants heading in a caravan to the US, cross the Suchiate River to Mexico, as seen from Ciudad Tecun Uman, Guatemala, Nov. 2, 2018.
Salvadorean migrants heading in a caravan to the US, cross the Suchiate River to Mexico, as seen from Ciudad Tecun Uman, Guatemala, Nov. 2, 2018.

WASHINGTON - Fears that Middle Eastern terrorists affiliated with Islamic State (IS) are trying to sneak into the United States from Mexico appear to be overblown.

U.S. counterterror officials tell VOA while they do have concerns about vulnerabilities along the southern border with Mexico, IS does not appear to have terrorist operatives embedded among the migrants making their way north.

"We do not see any evidence that ISIS or other Sunni terrorist groups are trying to infiltrate the southern U.S. border," a senior counterterrorism official told VOA on condition of anonymity. The official used an acronym for the militant group.

The counterterrorism official did not address Shiite terror groups, like Iran-backed Hezbollah. U.S. intelligence officials have long warned of Hezbollah operatives in Central and South America connected to the trade of illegal drugs and weapons.

FILE - President Donald Trump speaks during a rall
FILE - President Donald Trump speaks during a rally at Southern Illinois Airport in Murphysboro, Illinois.

When asked just over a week ago if Middle Eastern terrorists were part of the migrant caravans, U.S. President Donald Trump implied there were.

"You're going to find MS-13, you're going to find Middle Eastern, you're going to find everything," he told reporters.

A day later Trump admitted, "There's no proof of anything," but insisted, "There could very well be."

"I think there's a very good chance you have people in there," he added.

U.S. homeland security officials have said they arrest or stop, on average, about 10 terrorists a day from entering the country, though they have not specified how many try to cross over from Mexico.

In recent days, Trump and other senior administration officials have sought to stoke fears, warning the caravans pose an imminent danger.

"It's like an invasion," the president said Thursday. "We have no choice. ... We will defend our border."

Department of Homeland Security Secretary Kirstjen
Department of Homeland Security Secretary Kirstjen Nielsen speaks during the daily briefing at the White House in Washington, June 18, 2018.

On Friday, Homeland Security Secretary Kirstjen Nielsen said some of the people in the caravans were "quite violent."

"By the time we're talking about Molotov cocktails and use of firearms, it's my duty to ensure our officers and agents are secure," Nielsen said.

"When I met with my counterparts in one of the countries in the region recently, they were very concerned because they had missing children," she added. "There were kidnappings."

Nielsen's comments appeared to build on fears raised in a statement from DHS late Thursday that said that more than 270 individuals in the caravans have criminal histories, including gang members convicted of violent assaults and sexual abuse.

The statement also pointed to public statements by Mexican and Guatemalan authorities who claim unidentified individuals have been paying or forcing women and children to the front of the caravans to use as human shields.

On Friday, Nielsen suggested as many as 15,000 people were now part of caravans moving north toward the U.S. border with Mexico. But most estimates put the number at closer to 3,500 and shrinking. It will most likely take weeks before the first of the caravans reaches the U.S. border.

Asked about the potential for fighting to break out at the border, especially with the addition of active-duty military troops in a supporting role, Nielsen said border guards and agents would defend themselves.

"We have over 800 instances last year where they were attacked by those coming across the border," she said. "Our rules of engagement are transparent and clear and posted online."