While it is impossible to know how many firearms are illegally smuggled into Mexico in a given year, about 87 percent of firearms seized by Mexican authorities and traced in the last 5 years originated in the United States, according to data from Department of Justice's Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). According to U.S. and Mexican government officials, these firearms have been increasingly more powerful and lethal in recent years. Many of these firearms come from gun shops and gun shows in Southwest border states.