The number of migrants apprehended crossing the southern border illegally dropped by more than 37,500 in June, the first month-to-month decline since apprehensions began skyrocketing six months ago.Border Patrol agents apprehended 94,487 people crossing the border between ports of entry in Texas, New Mexico, Arizona, and California in June after capturing 132,000 migrants at the southern border the previous month, the Washington Examiner reported Tuesday.While the official figures have not yet been released, Acting Secretary of Homeland Security Kevin McAleenan estimated during a recent press conference that June saw a 25 percent decline in apprehensions. The numbers reported by the Examiner indicate a 28 percent decline.McAleenan credited President Trump's recent tariff threat with prompting increased border enforcement by Mexican officials. But the weather may also have played a role as apprehensions usually drop off from spring to summer due to dangerously hot temperatures.In early June, Mexico agreed to deploy troops to its border with Guatemala to stem the flow of Central American asylum-seekers traveling through Mexico to the U.S. The concession was extracted after Trump threatened to impose a 5 percent tariff on all Mexican goods entering the U.S. if its government failed to slow the influx of migrants that has overwhelmed American detention capabilities at the border in recent months.Mexico has, however, resisted the Trump administration's demand that they adopt a “safe third country” policy that would require all asylum-seekers who travel through Mexico to apply for asylum in Mexico before trying to enter the U.S.Mexican officials did agree to the administration's Migrant Protection Protocols, which require that certain asylum-seekers remain on the Mexican side of the border while their U.S. asylum claims are being adjudicated.