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HELENA, Mont. (AP) A criminal investigation is under way in Helena, to identify the source of chemical contamination in the city sewer system.

Public works director John Rundquist says someone is dumping chromium into the system.

When the chromium is in the sewage treatment plant, it kills bacteria that eat nitrogen and the treatment plant then releases excessive ammonia into Prickly Pear Creek, putting acquatic life at risk. Ammonia released into the creek has been more than five times the authorized amount.

The criminal investigation involves the U.S. Environmental Protection Agency, the Montana Department of Environmental Quality and the Helena Police Department.

Information from: Independent Record, http://www.helenair.com (Copyright 2008 by The Associated Press. All Rights Reserved.) APNP 11-22-08 1230CST | save this article / add to your favorites list