WASHINGTON COUNTY, Va. -

A clogged manhole caused a sewage spill into Little Creek in Bristol, Virginia.

We've learned six ducklings that were taken to a wildlife rehabilitation center after being rescued from the spill did not survive. When the ducks were trying to clean themselves, they may have ingested an oily substance found on their backs.

The ducks were rescued from Little Creek in Bristol, Virginia after some sort of spill killed fish and other aquatic life in the creek. "After probably five baths on each duck, we got the majority of whatever it was off of them," wildlife center director Dianne Andis said.

Andis told us that in an effort to clean themselves of the foreign substance, the ducklings probably ingested too much of the substance. "They didn't make it, sadly. We thought they were going to. We felt fairly certain that they were going to, but either the stress or whatever it was got on them did them in," she says.

"They appeared to have some sort of an oily-feeling substance on the back of the small ducks. The adult ducks didn't seem to be impacted," Alex Sneed with the Department of Enivironmental Quality said.

So what was the cause of the clogged sewer that caused the spill? The Department of Environmental Quality is still investigating, but they have an idea. "We have since learned that the manhole was clogged. The manhole that overflowed was clogged with oil and grease of some type," Sneed said.

As the investigation continues, recent rain showers may have helped alleviate some of the pollution. "Little Creek has probably got a higher flow, a greater volume of water traveling down it. It will probably be working to push this stuff on through if its not already gone," Sneed said.

We are continuing to get reports that more adult ducks are getting the unknown substance on them, but cannot be captured to be cleaned.