CHICAGO  —  The state of Illinois sued the Dave Matthews Band (search) on Tuesday for allegedly dumping up to 800 pounds of liquid human waste from a bus into the Chicago River, dousing a tour boat filled with passengers.

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

"Our driver has stated that he was not involved in this incident," band spokesman John Vlautin said in a statement. He said the band "will continue to be cooperative in this investigation."

According to the lawsuit, on Aug. 8 a bus leased by the band was heading to a downtown hotel where members were staying. As the bus crossed the Kinzie Street bridge (search), the driver allegedly emptied the contents of the septic tank through the bridge's metal grating into the river below.

More than 100 people on an architecture tour were showered with foul-smelling waste. The attorney general's office said no one was seriously injured.

"This incident may be unique, but that does not lessen the environmental or public health risks posed by the release of at least 800 pounds of liquid human waste into a busy waterway and onto a crowded tour boat," Attorney General Lisa Madigan (search) said in a statement.

After the incident, the boat's captain turned the vessel around and took passengers back to the dock. Everyone received refunds, and the boat was cleaned with disinfectant.