American troops now have the authority to detain and search undocumented migrants in New Mexico, a role service members have not held before at the southern border, U.S. Northern Command said Monday.

Northcom said troops “have been delegated the authority” to conduct security support operations in the New Mexico National Defense Area (NMNDA), a zone that runs along the U.S.-Mexico border now considered part of the Army’s Fort Huachuca in Arizona.

The authorization means service members can now temporarily detain and search trespassers, provide medical assistance and implement crowd control on the military-controlled land until appropriate law enforcement can take custody of an individual, according to a statement from Northcom, the command leading military efforts in the Trump administration’s crackdown on illegal immigration.

Troops also may assist with setting up temporary barriers, signage and fencing if requested, Northcom said. 

“Through these enhanced authorities, U.S. Northern Command will ensure those who illegally trespass in the New Mexico National Defense Area are handed over to Customs and Border Protection or our other law enforcement partners,” Northcom Commander Gen. Gregory Guillot said in a statement. 

He added that Joint Task Force-Southern Border, the military task force charged with supporting border security, “will conduct enhanced detection and monitoring, which will include vehicle and foot patrols, rotary wing, and fixed surveillance site operations.”

The new authorization comes after President Trump on April 11 directed the control of the Roosevelt Reservation area in New Mexico be transferred from the Department of the Interior to the Defense Department for a period of three years to support Border Patrol.

The transfer, which made the strip of land part of an Army installation, effectively allows the administration to bypass a federal law that prohibits American troops from carrying out domestic law enforcement on U.S. soil.

The move is a significant shift in the military’s role at the border, with troops over the last several administrations only supporting law enforcement agencies and not meant to come into contact with individuals crossing the border.

Guillot last month told lawmakers that the 6,500 service members at the southern border were supporting Customs and Border Protection and “are not currently doing any detentions.”

But that is expected to change with Trump’s new authorization, with plans to increase the area within which troops can detain and search migrants. 

White House press secretary Karoline Leavitt told reporters on April 15 that the new national defense area spans more than 170 miles across the border in New Mexico, and “in the coming weeks, this administration will add more than 90 miles in the state of Texas.”