LAWRENCE, Kan. (AP) — Toxins from a large algae bloom in a northeast Kansas reservoir wound up in the Kansas River, a major drinking-water source, but the toxins weren’t present in the water after it had undergone standard treatments, according to a study by the U.S. Geological Survey.

The study, conducted in September and October 2011, involved testing for algae toxins in samples from along about 170 miles of the Kansas River, from the Milford Reservoir to the Kansas City area. It was prompted by concerns about water releases from Milford Reservoir during a large algae bloom last summer. Releases from the reservoir head into the Kansas River, which provides drinking water for about 800,000 people in eastern Kansas.