The FDA shunned those calls, but admitted it had released inaccurate information on what chemicals were found in which top selling products.
As worried parents called manufacturers looking for guidance about the presence of melamine and a key byproduct in U.S.-made formula, the FDA reiterated its position that the baby food is safe and parents should continue feeding it to their babies, contending the extremely low levels of contamination do not present a health danger.
Also, a spokesman for one major manufacturer criticized the FDA for its release of the inaccurate information.
"We're getting inundated by calls from moms confused about the situation," said Pete Paradossi, a spokesman for Mead Johnson, one of the three major manufacturers of U.S.-made formula involved in the problem detections.
Melamine is the industrial chemical found in Chinese infant formula - in far larger concentrations - that has been blamed for killing at least three babies and making at least 50,000 others ill.
The FDA and said the melamine contamination in U.S.-made formula had occurred during the manufacturing process, whereas melamine was intentionally added to the Chinese products. U.S. Manufacturers say their products are safe.
"The levels that we are detecting are extremely low," said Dr. Stephen Sundlof, director of the FDA's Center for Food Safety and Applied Nutrition. "They should not be changing the diet. If they've been feeding a particular product, they should continue to feed that product. That's in the best interest of the baby."
Part of the confusion Wednesday stemmed from the FDA's own statements.
While proclaiming that the very low concentrations detected of melamine and a similar compound called cyanuric acid pose no health danger to infants, the FDA has maintained it is unable to identify any exposure level of melamine in infant formula "that does not raise public health concerns."
Further complicating the situation was inaccurate data that FDA released to The Associated Press, which was disclose the formulas' brand names in an investigative report Tuesday.
A spreadsheet the AP obtained from the FDA under a Freedom of Information Act request stated that Mead Johnson's infant formula powder, Enfamil LIPIL with Iron, contained traces of melamine.
On Wednesday, FDA spokeswoman Judy Leon said that spreadsheet contained an error - that the FDA had incorrectly switched the names of the Mead Johnson product with Nestle's Good Start Supreme Infant Formula with Iron. That meant, Leon said, that the Nestle's Good Start had melamine while Mead Johnson's Enfamil had traces of cyanuric acid.
The FDA said last month that the toxicity of cyanuric acid is under study, but that in the meantime it is "prudent" to assume that its potency is equal to that of melamine.
Problems with melamine-spiked formula surfaced this fall in China, where unscrupulous manufacturers intentionally dumped it into watered-down milk to falsely elevate protein levels. The concentrations in China were as much as 2,500 parts per million - about 10,000 times greater than what the FDA found in the U.S.
The FDA said there have been no reports in the United States of human illness from melamine. The chemical, which legally can be used in product packaging and a solution to clean manufacturing equipment, can bind with other chemicals in urine, potentially causing damaging stones in the kidney or bladder and, in extreme cases, kidney failure.
Mead Johnson spokesman Paradossi said he was frustrated that the FDA had provided inaccurate information for worldwide distribution by the AP. He said the FDA informed his company of the test results, as well as the inaccurate disclosures only Wednesday, during an emergency conference call the agency staged with major manufacturers and the industry's trade group. During a similar call Monday, the FDA told the industry about the upcoming AP investigative report.
Nestle did not returns calls seeking comment Wednesday.
At the same time, Illinois Attorney General Lisa Madigan called on the state's public health department and the FDA to recall both the Nestle and Mead Johnson products - and urged the companies to take that step regardless of what any government agency does.
Madigan also criticized the FDA's handling of its test results.
"The agency apparently withheld the results of its testing from the public for over three weeks, and then only disclosed the information in response to a FOIA request by The Associated Press," she wrote in a letter to Michael Leavitt, the secretary of the U.S. Department of Health and Human Services, which oversees the FDA.
As for possible consideration of a recall, the FDA's Leon said: "The agency would only seek to remove a product on the basis of a risk, based on scientific evidence. That's not what we're talking about here."
Consumers Union said that the FDA's assurances are of small comfort to parents and caregivers.
"The FDA originally said there was no safe level for these contaminants in infant formula. So this formula is contaminated," said Jean Halloran, the group's director of Food Policy Initiatives. "It is very disturbing to us that no recall has been requested."
She urged the FDA "to immediately make public all of the results of its tests for melamine contamination in food," even those with levels below what would trigger agency action."
Rep. Bart Stupak, D-Mich., a frequent critic of the FDA, also has called for recalls.
During a series of calls with formula manufacturers starting Monday - put together hurriedly, according to several participants, as the AP was preparing to publish its story - the FDA has told manufacturers it has taken 230 samples of various products, including pediatric supplements and ingredients used in infant formula. Leon said that 87 of those samples are of infant formula, and that 77 of those have been analyzed.
Under the corrected information she relayed Wednesday, the results were:
Separately, a third major formula maker - Abbott Laboratories, whose brands include Similac - told AP that in-house tests had detected trace levels of melamine in its infant formula. Those levels were below what FDA found in the other formulas, an Abbott spokesman said, and below any nation's safety guidelines.
The three firms - Abbott Laboratories, Nestle and Mead Johnson - manufacture more than 90 percent of all infant formula produced in the United States.