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The search warrant was executed at 9:03 p.m. Friday at the storage unit, 665 Big Timber Road, according to police. The warrant and search came from information received by Homeland Security Investigations and is part of an ongoing investigation, officials said.
The Kane County Sheriff's Office Bomb Squad was also called to the scene to secure the grenades, police said.
Officers in the Elgin Police Department's Special Investigations Division and federal agents identified the unit's renter Juan Mexicano, 31, of Addison, who was taken into custody without incident, according to police.
Mexicano's next court date is set for Aug. 31 at the Kane County Judicial Center.
According to Kane County court documents, the guns recovered included a Colt AR-15 SP1 model .223 caliber rifle, two unknown model .233 caliber rifles, an MP28 Schmeisser, and a .45 caliber Thompson submachine gun.