CHATTANOOGA, Tenn. (AP) -- At least 13 common drugs, including caffeine, several antibiotics, antidepressants and substances designed to lower human cholesterol levels, were found in test samples of Tennessee River water.

Sean Richards, a professor of biological and environmental sciences at the University of Tennessee at Chattanooga, is taking the samples as part of a study conducted with another UTC professor to gauge pharmaceutical concentrations.

A landmark study published by the U.S. Geological Survey in 2002 and an Associated Press investigation last March delved into the issue, but neither included studies in Tennessee.

The UTC team has spent 2 1/2 years analyzing river water samples from Knoxville to Chattanooga. Richards said so far the drugs have been detected here in minuscule proportions, the same as in other areas of the country.

EPA officials have said they believe the water supply is safe, but are looking into water standards for pharmaceuticals.

(Copyright 2008 by The Associated Press. All Rights Reserved.)