In Chicago, police discovered a warehouse full of millions of dollars' worth of stolen, high-end shoes, including Nikes and Yeezys, CBS News Chicago reports.

Authorities called the theft ring – which targeted freight trains – a sophisticated national operation. Law enforcement officials said the massive bust was from an investigation by the Lyons Police Department following reports of a recent cargo theft. That led investigators to the warehouse where “$5 million in merchandise, minimum” was discovered, Lyons Police Chief Tom Heroin said.

Officials said the thieves conducted several railroad cargo thefts across the country and then housed the merchandise (consisting of UGG products, Nike, Adidas, Supreme and more) in the warehouse.

Towers of shoe boxes were stacked in the warehouse located in Chicago’s Austin neighborhood, including limited edition footwear. The thieves would advertise the merchandise on social media and by word of mouth. Unsuspected retailers would go to the site, make a deal, without any knowledge that the goods were stolen.

During this ongoing investigation, two people have been charged, while several other people are still being investigated.

Several railroad companies and the Illinois Attorney General's Office already suspected suspicious activity at the warehouse due to the surge in nationwide cargo thefts.

"What they would do is they'd commit these cargo thefts, like from Memphis, Tennessee. They'd re-label it, and they would ship it here. They would unpackage it, repackage it, and it's a 100 percent markup because they got it all for nothing," Heroin said.