Federal biologists checking the upper Potomac River have found that abnormalities in bass there are even more widespread than they'd earlier reported. But they're no nearer to understanding what's causing it.

At least 82 percent of male smallmouth bass and 23 percent of the largemouth bass had immature female germ cells in their reproductive organs, according to a release by the U.S. Fish and Wildlife Service and U.S. Geological Survey.  Abnormalities also were found in some female fish.

(Those who watched the PBS documentary "Poisoned Waters" Tuesday night saw researchers collecting bass for study and sampling the Potomac water. They also heard scientist Vicki Blazer say she probably wouldn't drink water from the Potomac -- where many Washingtonians get their water -- because of uncertainty about what's in it, even after it goes through municipal processing for drinking.)

Scientists think the abnormalities may be linked to hormone-like chemicals in medicines and a variety of consumer products. They had theorized that the contaminants, known as endocrine disruptors, were getting in the river from wastewater treatment plants that discharge into it. But the problems are not limited to areas downstream from sewage plants, they found. 

Anglers and fisheries officials, meanwhile, say the bass downriver are abundant and seem healthy. The largemouth at left, captured visually by Sun photographer Doug Kapustin, came from Mattawoman Creek, a Potomac tributary. 

Officials now say they are looking to see if multiple chemicals, and not just those from sewage plants, may be responsible for the intersex conditions.  They're also expanding their search for fish with abnormalities to the rest of the Potomac and to other East Coast rivers.

For more on the issue, go here.