The Fairmont Chicago confirmed the incident happened at a DNC-related breakfast at their hotel Wednesday morning.
According to Chicago police, several women allegedly entered the hotel and began putting "unknown objects" onto tables that held the food. They then left the area, police said.
Sources told ABC7 Chicago the women put maggots on the tables.
Police said one person was treated and released at the hotel, but did not say what for.
The hotel released a statement, saying in part, "We can confirm that a group of individuals caused a disruption at a DNC-related breakfast event at our hotel this morning. We are grateful for the swift response of law enforcement. The safety, security, and well-being of our guests and staff are our top priorities."
Along with CPD, the FBI is assisting in the investigation. No further information was immediately available.