Kansas City, Mo. ? A federal study shows that toxins from a large algae bloom in a Kansas reservoir wound up in the Kansas River, a major drinking water source for about 800,000 residents in eastern Kansas.

The study by The U.S. Geological Survey also showed, however, that the toxins weren’t present in the water once it had been treated for consumption.

The USGS study was conducted last year on the Kansas River from the Milford Reservoir to the Kansas City area. It came after a massive summer algae bloom at the reservoir prompted concerns about the algae toxins making their way into the river from reservoir releases.

The USGS says it’s started a program with regional public drinking water suppliers to monitor algae toxins in the Kansas River.