The Enfamil recall of 2011 just got bigger: besides Walmart, at least one more retailer, Supervalu, joined its decision to pull Enfamil off its shelves.

Supervalu said it pulled the lot number that has been identified off our shelves out of an abundance of caution, according to the Wall Street Journal.

Both Walmart and Supervalu are holding the baby formula until further notice from health authorities.

A Walmart spokesperson said customers can return or exchange their Enfamil purchases if they chose to, according to Business Week.

The recall was sparked by the death of a Missouri infant who was fed an Enfamil formula purchased from Walmart that carried the lot number ZP1K7G, reported the Wall Street Journal. The infant's death happened on Sunday and Walmart began recalling Enfamil on Monday from more than 3,000 stores.

The infant died from Cronobacter, a rare bacterial infection, according to preliminary tests, reported the Christian Science Monitor.

However, health officials have not indicated that Enfamil was at fault. That is, it remains unclear if the infant died from Cronobacter contracted through Enfamil ingestion or another source. Walmart, Supervalu and any other retailers that may have pulled Enfamil off their shelves have done so voluntarily (health officials have not recommended any recalls yet).

Mead Johnson Nutrition, the maker of Enfamil, claims it previously tested the batch sold to the deceased infant and did not find any Cronobacter.

Investors of Mead Johnson Nutrition, however, are clearly concerned. While the broad stock market rallied on Thursday, shares of Mead Johnson plunged 10 percent. Earlier in the trading session, it was down as much as 20 percent, according to the Wall Street Journal.

In the past, bacterial infections like Cronobacter have been linked to various baby formulas, reported the Wall Street Journal.