Feb. 16 (UPI) — U.S. Customs and Border Protection said border patrol agents found a catapult attached to a U.S.-Mexico border fence designed to hurl drugs into Arizona.

Douglas Station Border Patrol agents made the discovery on Friday when they saw several people on the Mexican side of the border quickly retreat once the agents approached.

“When agents arrived at the fence they found a catapult system attached to the south side of the border fence. They searched the area and located two bundles of marijuana” weighing more than 47 pounds combined, U.S. CBP said in a statement on Tuesday.

U.S. agents contacted Mexican law enforcement authorities, who launched an investigation. U.S. Border Patrol agents dismantled the catapult system, which Mexican authorities seized.

U.S. President Donald Trump has vowed to build a wall, with some fencing, along the U.S.-Mexico border to prevent the flow of illegal immigration and drugs into the United States.