The city of Phoenix is declaring its water supply clean and drug free.

Tests were conducted by an independent lab at each of Phoenix's six water-treatment plants. And Mayor Phil Gordon says the results showed no traces of pharmaceuticals while meeting all standards of the Environmental Protection Agency.

The city tested the water after a series of stories by The Associated Press said that pharmaceuticals have been identified in Lake Mead's water. Some of the lake's water reaches the Phoenix area by way of the Central Arizona Project canal.

The AP report said the chemicals were in tiny quantities.

Drugs are thought to enter the water supply after being ingested by people and passed into the sewage system. Other drugs get flushed into the system. No one knows whether exposure to small quantities of these drugs can cause problems.

The AP has the full story.