What happens on a rock star's tour bus generally stays there, but the Dave Matthews Band's dirt made a public appearance earlier this month in Chicago.

The band is being sued by the state of Illinois for allegedly dumping up to 800 pounds of liquid human waste from its bus into the Chicago River on August 8, according to The Associated Press.

The suit, filed Tuesday, claims that a boat with more than 100 people on an architecture tour was soaked with sewage when the driver emptied the bus' septic tank through the Kinzie Street bridge's metal grating into the river. According to the AP, the attorney general's office said no one was seriously injured by the falling waste, and the boat's captain quickly took the ship back to shore and handed out refunds to passengers before disinfecting the boat.

Dave Matthews Band spokesperson John Vlautin said of the incident, "Our driver has stated that he was not involved in this incident," and added that the band "will continue to be cooperative in this investigation."

The lawsuit seeks $70,000 in civil penalties and charges the band and one of its drivers with violating state water-pollution and public-nuisance laws.