The package was on the Riverwalk near Michigan and Wacker.
As a precaution, pedestrians were not allowed on the Michigan Avenue Bridge or the Riverwalk.
Police dogs were used to search the area. The fire department says it turned out to be drain cleaner in a plastic bag.
Police say the move to close the bridge to foot traffic was a precautionary measure after they received calls of a suspicious package early Monday afternoon.The bridge reopened to pedestrians around 1:15 p.m.