MIDDLE AMANA, Iowa (AP) –  A private utility providing water to 850 customers in east-central Iowa’s Amana Colonies has stopped using three wells because tests show a nitrate level above federal safety standards. The Amana Society Service Co. instead is using water from three other wells that have tested as safe. The Gazette reports that the company has warned customers to avoid giving tap water to infants or nursing mothers. Nitrate in drinking water has been linked to blue-baby syndrome. Officials don’t know why the nitrate levels rose in late fall. Spring usually is the season for elevated nitrate as melting snow washes fertilizer off farm fields.