Immigration officials have charged three men with smuggling more than 28,000 rounds of ammunition along the Southwest border.
One of the men is a U.S. citizen, the other two are Mexican nationals, ICE officials said.
The break for authorities began when they put a Tuscon residence under surveillance.
Agents conducting the house surveillance noticed a white minivan leaving, and heading toward Nogales. The agents, who are with the ICE’s Homeland Security Investigations unit, arranged for the Arizona Department of Public Safety to stop the van “based on probable cause,” according to federal authorities.
During that stop, authorities found more than 9,000 rounds of ammunition, ICE officials said.
Information from the traffic stop prompted agents to obtain a search warrant for a search of the Tuscon home, where they seized an additional 19,750 rounds of ammunition, one .223 semi-automatic rifle and two .22 caliber rifles, according to ICE officials.
"Weapons smuggling along the Southwest border clearly contributes to ongoing public safety challenges in Mexico," said Matt Allen, special agent in charge of ICE HSI in Arizona. "One of my top priorities is working with law enforcement partners like DPS to stem the flow of weapons and ammunition south of the border."
Authorities arrested Alejandro Ruiz-Escalante, 23, and Christian Gallegos-Arizmendi, 19, both citizens of Mexico, and charged them with weapons smuggling.
Federal agents also arrested Jesus Lopez, 35, a U.S. citizen with an extensive criminal history and outstanding warrants for domestic violence and drug possession. Lopez is also facing federal weapons charges. All three suspects had their initial appearance in federal court in Tucson Wednesday.
Elizabeth Llorente is Senior Reporter for FoxNews.com, and can be reached at Elizabeth.Llorente@Foxnews.com. Follow her on Twitter @Liz_Llorente.