"My office has been informed that this week an armed group near Sunland Park, New Mexico, has arrested nearly 300 people," said Attorney General Hector Balderas in a written statement. "These individuals should not seek to exercise authority reserved for law enforcement."
Online videos allegedly showing migrants from the United Constitutional Patriots group and handed over to the US Border Patrol were quickly condemned by the American Civic Union of New Mexico.
CNN appeals to the United Constitutional Patriots to comment.
Governor's office threatens migrants "unacceptable"
A statement on the Facebook page of the United Constitutional Patriots describes the group as "Americans who believe in the Constitution and the rights of every American who works for the rights of the United States and contributes to America's security."
"We're only here to support the border patrol and show the public the reality of the border," spokesman Jim Benvie told the New York Times, noting that his group has been near El Paso for the past two months outsourced.
Benvie's group "plans to stay at the border until President Trump's proposed extended wall is established or Congress changes immigration laws to make it harder for migrants to seek asylum," the Times reported.
However, it is rare to see a video of an armed group imprisoning migrants on the US side of the border.
A spokesman for the New Mexico government, Michelle Lujan Grisham, said the state and local authorities are investigating the matter.
"They have not been authorized by our office or anybody else, and we are working actively with the AG, the state police, and the local police to determine what is going on and what can and will be done," said the spokesman for Tripp Stelnicki the governor. "It is completely unacceptable that migrant families are threatened or threatened in any way."
CBP says it will not tolerate civilians interfering with law enforcement matters
Asked about the United Constitutional Patriots and the videos that the group put online, a spokesperson for the US Customs and Border Guard refused to comment on the group or social media posts, but said the agency "does not endorse private groups or organizations that so wish." Enforcement measures in your own hands. "
"Interference by civilians in law enforcement matters could have public safety and legal consequences for all concerned," the spokesman said in a written statement, referring suspects suspected of illegal activity, number 911 or directly with the agency. "Border operations are complex and require well trained professionals with adequate resources to protect the country."
Peter Simonson, executive director of the ACLU of New Mexico, told CNN that while militia groups were patrolling the border, these groups now feel empowered by the rhetoric they hear from the White House.
"We acknowledge that these groups have the freedom to unite, assemble, freedom of speech, and our laws on state weapons that can give them weapons," Simonson said. However, the main concern of the ACLU is that private armed citizens "are committed to justice and do not allow the federal authorities to do their job".
"These people are armed, their intentions are misguided and they certainly have no education, let alone any authority – to carry out arrests and long-term arrests of people crossing the border," Simonson said. "We're worried that this is a potentially explosive situation, we're worried that someone's going to get hurt."
CNN's Carma Hassan and Paul P. Murphy have contributed to this report.