WEBSTER CITY – Webster City officials are offering a reward for information about a petroleum spill that was found in the Boone River there Thursday afternoon.

Officials said the sheen they saw on the river near Nokomis Park in Webster City was a petroleum product such as diesel fuel or oil, based on its smell, look and iridescence.

The Iowa Department of Natural Resources and Webster City Police Department were notified.

The substance has since dissipated.

Officials are asking citizens for assistance in determining the source of the contamination and the individual or individuals responsible. A $300 reward is being offered for information leading to an arrest if it is determined that this was an intentional spill.

Those with information are asked to contact the Webster City Police Department at (515) 832-9166.