(CNN) When 400 guns go missing, there's cause for concern -- understandably.

For two days, agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and local law enforcement searched for two men who stole that many weapons from a UPS facility in Memphis.

The burglary occurred Sunday. Officials say two men drove up in a U-Haul truck and made off with about 400 guns

On Tuesday, the ATF's Chicago office said "hundreds of guns" stolen from the distribution center have been recovered in Illinois.

The office said it has one person in custody, but it's looking for a second.

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