The Food and Drug Administration said Tuesday that traces of the industrial chemical melamine have been detected in samples of top-selling US infant formula, but the products are still safe.

“The levels that we are detecting are extremely low. 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,” Dr. Stephen Sundlof, director of the FDA’s Center for Food safety and Applied Nutrition, said.

Melamine, a toxic chemical used for producing plastics and fertilizers, was previously detected in Chinese milk. Four babies died and more than 50,000 took ill after drinking formula milk tainted with the chemical. If ingested, melamine can lead to the formation of kidney stones and crystals and related complications.

Melamine was also found in several samples of dietary supplements that are made by some of the same manufacturers who make formula, the FDA said. The name of the manufacturer was not made public. Abbott Laboratories, Nestle and Mead Johnson manufacture more than 90 percent of all infant formula produced in the United States.

Industry trade group the International Formula Council released a statement trying to reassure consumers.

“Infant formula manufactured in the United States remains safe and nutritious,” the statement read. “U.S. infant formula products meet the highest standards and specifications.”

This month, the FDA announced it was limiting the import of all dairy products from China until they have been proved free of melamine.