Update, 6:30 p.m.: The brown substance is rust and dirt, DNAInfo reports.
Original post, 4:49 p.m.: Something gnarly leaked into the Chicago River Thursday morning, and no one is quite sure what it was. A spokeswoman for the city's Metropolitan Water Reclamation District told the Chicago Tribune that the group is "investigating the discoloration," which is not generally a phrase with positive implications, whether regarding one's own personal health or the health of a major-city waterway and tourist attraction. The DNAInfo site was unable to get an answer about the brown substance's origin from the city's Department of Streets and Sanitation, its Department of Water Management, or the Illinois Environmental Protection Agency.
In 2004, a Dave Matthews Band tour bus emptied its septic tank while crossing a grated bridge over the river, drenching tourists on a boat below in what the Tribune described as "a downpour of foul-smelling, brownish-yellow slurry" and also described as "800 pounds of human waste."