The director of investigations for a watchdog group recently disclosed that a migrant caravan moving from Central America to the United States is being used for human trafficking. He also confirmed sightings of non-Central American nationals and alleged gang members.

Migrant caravans that travel from Central America to the United States' southern border have turned out to be a convenient way to conceal some of the worst of international crimes: child smuggling.

Seven unaccompanied children have been reportedly saved from a second caravan, which just left Guatemala City, by Guatemalan law enforcement officers, according to a report by Judicial Watch published Thursday. The second caravan consists of some 1,500 migrants, while the first, much larger caravan of 7,500 is currently moving through Mexico, some 1,100 miles from the US border.

According to the report, the children have been taken into custody by authorities and their health is being assessed. In the meantime, the smugglers have been arrested by law enforcement.

"This caravan deal presents an opportunity for incredible criminal activity," said Chris Farrell, Judicial Watch's director of investigations.

Farrell said that he saw people with gothic-lettered "MS" tattoos among the migrants in the caravan, typically a sign of affiliation with the "MS-13" criminal group.

He also confirmed he saw migrants from non-Central American nations — people that US Border Patrol agents reportedly refer to as "special interest aliens."

US President Donald Trump has declared the caravans a national emergency, while the US Department of Defense reported it is preparing to send 800 US troops to reinforce the southern border.

On Tuesday, the US Department of Homeland Security said on Twitter it had confirmed sightings of individuals in the first caravan "who are gang members or have significant criminal histories."

.@DHSgov can confirm that there are individuals within the caravan who are gang members or have significant criminal histories. — Tyler Q. Houlton (@SpoxDHS) 23 октября 2018 г.

​"Citizens of countries outside Central America, including countries in the Middle East, Africa, South Asia, and elsewhere are currently traveling through Mexico toward the US," the department said. "Stopping the caravan is not just about national security or preventing crime, it is also about national sovereignty and the rule of law. Those who seek to come to America must do so the right and legal way."