More than 100 people have reported getting sick after attending a conference at the Hilton Chicago hotel at 720 S. Michigan Ave.

The city's Department of Public Health is investigating. Those people attended the La Leche League International 50th anniversary conference. It was held last Friday through Monday.

Health officials say it is too early to tell what caused the illnesses, but they appear to be the result of a norovirus, which is common and is similar to the flu.

Health officials say the kitchens at the hotel passed an inspection and hotel employees are cooperating with the investigation.

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