Cameron says the spill is considered medium-sized on a scale that ranges from minor to major. The medium-sized designation applies to inland leaks between 1,000 and 10,000 gallons of oil, Cameron said.
Officials had no more immediate description of the spill or its size.
"We are working with officials from Duke Energy to determine the extent," Cameron said.
Local, state and environmental agencies also were at the scene Tuesday, and the Coast Guard said Duke has assumed responsibility for spill cleanup.
Ohio EPA spokeswoman Heidi Griesmer said the water quality alert system for the Ohio River was activated and all river drinking water intakes in Ohio were sealed off. The Greater Cincinnati Water Works shut down its water intakes around 12:50 a.m. and monitoring of the water entering the system prior to shut-down showed no contamination, Griesmer said.
The Kentucky Department for Environmental Protection had a representative at the site, but no additional information was immediately available, said department spokeswoman Ricki Gardenhire.
Peter Tennant, executive director of the Ohio River Valley Water Sanitation Commission, says drinking water intake valves were closed for both Northern Kentucky and Cincinnati and probably would remain closed until it is deemed safe to open them.
He said both sides of the river have the capacity to operate off their stored water supplies for at least a couple of days.