The videos posted over the last several days show members of United Constitutional Patriots ordering family groups as small as seven and as large as several hundred to sit on the dirt with their children, some toddlers, waiting until Border Patrol agents arrive.
Customs and Border Protection said it "does not endorse or condone private groups or organizations that take enforcement matters into their own hands."
"Interference by civilians in law enforcement matters could have public safety and legal consequences for all parties involved," the agency said on its Twitter account.
#CBP does not endorse or condone private groups or organizations that take enforcement matters into their own hands. Interference by civilians in law enforcement matters could have public safety and legal consequences for all parties involved.— CBP (@CBP) April 19, 2019
Jim Benvie, a spokesman for the group, said members assist a "stressed and overstrained Border Patrol" and there are no issues with its actions. One video shows a Border Patrol agent arriving after the group tells a small group to sit and wait.
"We get along great with Border Patrol. They get along with us," Benvie said in a Facebook video. "We work together, and yadda, yadda, yadda."
Benvie said the group is legally armed for self-defense and never points guns at migrants. The posted videos do not show them with firearms drawn.
"We use verbal commands, we don't touch people. Our job is to slow them down...sit them down until Border Patrol can get over there," Benvie told El Paso television station KVIA.
United Constitutional Patriots operates in and around Sunland Park, New Mexico, a suburb of El Paso, Texas, and a popular spot for Central Americans to cross the border illegally because there is no physical barrier in some areas.
Larry Mitchell Hopkins, one of the group's leaders, was arrested Saturday on federal weapons charges, according to the FBI's Albuquerque field office. New Mexico Attorney General Hector Balderas said in a statement that Hopkins is a "dangerous felon who should not have weapons around children and families."
Armed civilian groups have been a fixture on the border for years, especially when large numbers of migrants come. But, unlike previous times, many of the migrants are children. In the Border Patrol's El Paso sector, which has suddenly emerged as the second-busiest corridor for illegal crossings after Texas' Rio Grande Valley, 86% of arrests in March were people who came as families or unaccompanied children.
New Mexico Gov. Michelle Lujan Grisham, a Democrat, said Friday that she was actively working with state and local police to address the armed groups. "Menacing or threatening migrant families and asylum-seekers is absolutely unacceptable and must cease," she wrote on Twitter.
We are actively working with @NewMexicoOAG as well as local and state police. Menacing or threatening migrant families and asylum-seekers is absolutely unacceptable and must cease. https://t.co/yYXf8G5m2O— Gov. Michelle Lujan Grisham (@GovMLG) April 19, 2019
The American Civil Liberties Union of New Mexico on Thursday wrote Lujan Grisham and state Attorney General Hector Balderas on Thursday, urging them to investigate the incidents, including what it said was the detention of nearly 300 people on Tuesday near Sunland Park.
"This has no place in our state: we cannot allow racist and armed vigilantes to kidnap and detain people seeking asylum," the ACLU wrote.
Mexico's Foreign Ministry released a statement expressing "profound concern about the activities of intimidation and extortion of migrants by groups of militias on the New Mexico border."
"This type of practice can lead to an abuse of the human rights of people who migrate or who request asylum or refuge in the United States," the statement continues. "For Mexico, the tasks of patrolling and security, apart from the legal structures of the federal government of that country, also constitute a risk to the human security of migrants."
ABC Owned Television Stations contributed to this report.