Nobody is going to be back working inside that building for a long time.
2-3 weeks minimum.
They've already announced at minimum the building will be closed tomorrow.
I think it'll be longer than 2-3 weeks. The Cook County building was closed for 3+ months if I remember right. The LaSalle Bank Building is considerably larger (takes up an entire city block in length, 3/4 of a block in width) than the Cook County building.