The Trump administration’s “zero tolerance” policy is deterring Central American migrants from traveling to the U.S., the Department of Homeland Security argued Thursday. The department cited an 18 percent drop between May and June of illegal immigrants who were either apprehended while crossing illegally or turned away as inadmissible at the southwest border.

“Following the implementation of the administration’s zero-tolerance policy, the June 2018 Southwest Border Migration numbers declined by 18 percent when compared to the previous month,” DHS press secretary Tyler Q. Houlton said in a statement issued Thursday afternoon.