Chicago Building Code Violation

[Patrick Howe]

I recently purchased a 3 unit building on the Northwest side of Chicago that I also occupy in June 2015. There is a single story addition on the rear of building with a master bed and bath. The addition appears to be 5-10 years old. I received a letter from the Chicago Building Department stating the addition is a violation due to never having a permit. The letter states I am responsible.

Wondering if anyone has dealt with this in the past. The previous owner clearly never got a permit for the work done when owned the property. Am I liable for any fines/permits or is the previous owner?

A side note: The plot survey given to me at closing included to he addition