Four men were arrested in a record-breaking drug bust after authorities seized over two and a half tons of methamphetamine in Southern California, officials said. 

Officials said a commercial 20-foot box truck passed through the U.S.-Mexico border just before 5 p.m. on Thursday. Law enforcement surveilled the truck as it drove to National City, California, just south of San Diego. 

When the truck stopped, the four men were reportedly seen unloading dozens of cardboard boxes from the truck into a Dodge van, according to the U.S. Attorney’s Office. Authorities apprehended the men, and upon investigating the boxes, discovered 148 bundles of substances that tested positive for methamphetamine.

There was over 5,000 pounds of the drug transported, officials said, making what is believed to be one of the largest methamphetamine seizures in San Diego County history.