Lakeside Alliance, the construction team, said in an email to the Chicago Tribune that the organization reported the incident to the police and "will provide any assistance required to identify those responsible.”

The alliance—a joint venture of Turner Construction Co., Powers & Sons Construction Co., UJAMAA Construction Inc., Brown & Momen Inc., and Safeway Construction Co.—is also offering a $100,000 reward to help find the responsible party.

”We have zero tolerance for any form of bias or hate on our worksite," the group added, noting that anti-bias training was part of the project's onboarding process and that the training was repeated during jobsite meetings. The pause in work will be used for "another series of these trainings and conversations for all staff and workers.” 

The Obama Foundation said in a statement that "this shameless act of cowardice and hate is designed to get attention and divide us. Our priority is protecting the health and safety of our workforce."

Construction of the privately financed center, set to open in 2025, is estimated to cost about $700 million, says the Chicago Sun-Times that cites recent documents released by the foundation.