National Guard troops deployed to the U.S.-Mexico border following President Donald Trump's April directive have freed U.S. Customs and Border Protection personnel to apprehend an additional 1,600 people illegally crossing into the U.S., CBP officials said.

The approximately 775 National Guard troops have also helped capture 1,000 pounds of marijuana and turn back 451 people who attempted to illegally cross the border, the Washington Examiner reported.

The extra personnel have allowed the CBP to focus on monitoring surveillance systems and being better equipped to make arrests, the report said.

Defense Secretary James Mattis stipulated Tuesday that National Guard officers do not perform arrests.

“Right now we are not having any contact with migrants,” he said.

CBP officials are prohibited from monitoring the Mexican side of the border. A National Guard official distinguished monitoring the Mexican side as a “more of an intelligence-collecting capacity.”

National Guard troops operate under a different legal authority and are not prohibited from monitoring the Mexican side of the border with binoculars, the official said.

CBP has reportedly sought additional assistance from the Department of Defense. The request is pending.