By Dana Kozlov

CHICAGO (CBS) — UPS headquarters might be in Atlanta, but for almost three months, hundreds if not thousands of pieces of its corporate mail were delivered to a small unassuming garden apartment in the Rogers Park neighborhood in Chicago.

That corporate mail included tens of thousands of dollars in business checks. According to court documents, it began with a simple unauthorized change of address form filled out by a Chicago man. Now, it’s the focus of a federal investigation.

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Apartment 2 at 6750 N. Ashland Av. became the address for UPS corporate headquarters in October, after the man who lives inside filled out a change of address form at a post office, according to a federal affidavit. UPS corporate mail then was redirected and delivered to the apartment.

Dushaun Spruce lives in that basement apartment.

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According to the affidavit, UPS security notified the U.S. Postal Inspection Service in January that its address had been changed. The affidavit stated 10 UPS business checks totaling $58,000 were eventually deposited into a bank account by a man who said he lives at that Rogers Park address. The bank provided security video of the man. A search warrant was then issued for the apartment.

Spruce said he did get some UPS mail, but claimed he never opened it. He said authorities interviewed him in January or February, and searched his apartment, but haven’t talked to him since then.

The mail carrier for the building told investigators he noticed and even personally delivered the large amounts of mail.

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A spokesperson for the post office declined to comment on why the change of address wasn’t flagged.