Wal-Mart has removed a powdered infant formula from more than 3,000 shops across the US after a newborn baby who consumed it died from a rare infection.
Tests are under way to see if there is a link between the formula and the death of the infant last weekend.
The government has not recalled Enfamil Newborn formula, and the maker said pre-shipment tests were negative.
The bacterium, Cronobacter sakazakii, is extremely rare but is dangerous to premature and newborn babies.
It is commonly found in plants such as wheat and rice.
Avery Cornett, from the town of Lebanon, in Missouri, died on Sunday after being removed from life support.
Missouri health officials have sent the formula to federal laboratories for testing.
In a statement, they warned that powdered infant formula was not sterile and it could be impossible to kill bacteria during production.
Those who purchased the formula with the specific lot number of ZP1K7G would receive a full-refund, Wal-Mart said.