(CNN) National Guard troops stationed along the US-Mexico border have contributed to 1,600 apprehensions of people crossing the border illegally and the capture of about 1,000 pounds of marijuana in their three-and-a-half weeks on the job, according to a Customs and Border Protection official.

The official said the National Guard troops have also contributed to 451 "turn backs," where individuals abandon an attempt to illegally cross into the US.

The official did not have comparison numbers available, so it was not possible to determine if those figures were substantially more than if National Guard troops had not been dispatched to the border.

There were roughly 38,000 apprehensions of people trying to cross the border illegally each of the past two months, according to data from the Department of Homeland Security. That's roughly 2.5 apprehensions per agent stationed at the border, though not all are in the field. Monthly apprehensions fluctuate with the season and other trends, and it is difficult to attribute changes to any one cause.

The official described the troops as a "force multiplier" and said they are are relieving Border Patrol agents from a variety of responsibilities that are not on the front lines, such as monitoring surveillance systems from control centers. That allows CBP to place additional agents on the ground where they can make arrests.

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