Up to 90 percent of the infant formula sold in the United States may be contaminated with trace amounts of melamine, the toxic chemical linked to kidney damage, according to recent tests. The FDA's test results, which the agency hid from the public and only released after the Associated Press filed a Freedom of Information Act request, showed that Nestle, Mead Johnson and Enfamil infant formula products were all contaminated with melamine.

The AP is also reporting that Abbott Laboratories conducted its own in-house tests that detected trace levels of melamine in its formula products. Together, these infant formula manufacturers make about 90 percent of the infant formula sold in the United States.

Prior to these test results being made public, the FDA had published a document on its website that explained there was no safe level of melamine contamination in infant formula. Specifically, the FDA stated, "FDA is currently unable to establish any level of melamine and melamine-related compounds in infant formula that does not raise public health concerns."

Once tests found melamine in U.S.-made formula products, however, the FDA changed its story. As of today, the FDA has now officially declared melamine to be safe in infant formula as long as the contamination level is less than one part per million (1 ppm).