Homeland Security Secretary Kirstjen Nielsen told Fox News that intelligence "absolutely" indicates that the migrant caravans traveling through Mexico to the United States include people from the Middle East and Southeast Asia.
"We absolutely see people from the Middle East, from southeast Asia, from other parts of the world," Nielsen said. "They are not just from Central America.
"We don't always know exactly who they are," she continued. "What I can tell you is we stopped 3,000 people last year at the southwest border who had patterns of travel similar to a terrorist. We call those special interest aliens."
Nielsen said the caravans appear to be organized and financed, and that the timing of their formation raises suspicions of their origin and motive.
The Homeland Security chief also said the migrants are using women and children as "barriers," sending them up front to frustrate military and police, and that the following caravans are "mostly single men."
This is important because: There is dispute about whether migrant caravans to the U.S. pose a threat, and about how many resources should be sent to the southern border to prevent illegal entry. Two Department of Defense officials told CNBC that President Donald Trump's decision to deploy thousands of troops to the southern border to handle incoming migrant caravans will cost $220 million.
As the number of migrants continues to grow, the perceived need for troops at the border will increase, as will the potential length of their deployment.
A fourth migrant caravan has crossed from Guatemala into Mexico, bringing the estimated total of migrants traveling through Mexico to the United States above 12,000, according to Mexico News Daily.
The most recent caravan crossed illegally into Mexico through the Suchiate River, turning down an offer from Mexican authorities to be given shelter if they entered legally and telling them they only want clear passage to the U.S., not to stay in Mexico.
Is this necessary? Trump has made it clear he believes the migrant caravans represent a foreign invasion of the United States, implying that the caravan consists of dangerous criminals and unspecified people from the Middle East.
However, a Pentagon assessment reportedly has determined that the caravan does not pose a risk to the country.
Members of the caravans have clashed with Mexican authorities as they make their way north from Central America, resulting in some injuries to police officers and at least one caravan member death.
The first caravan grew as large as about 7,000 people, but has reportedly shrunk by nearly half as people turn back or quit the journey in Mexico. A second caravan of about 1,000 migrants is also making its way through Mexico.
How many troops? More than 7,000 troops will be stationed in Arizona, California, and Texas to support Customs and Border Patrol. Trump indicated last week that as many as 15,000 troops could be deployed — about three times as many troops as there are migrants still pushing north.
With the lead caravan possibly more than a month away from the U.S. border, the number of migrants that actually arrives at the U.S.-Mexico border is likely to be much smaller.
