I had same experience with Enfamil. I called their customer service, they asked an Express pickup service to come to my house to pick up the powder formula, at their charge, then send it to their lab for testing. They then sent me a lab report within a week explaining the cause. In my case, it was nothing to worry, it was generated by production line when temperature was high. Btw, they later sent me one unopened can of formular back.