(Reuters) - U.S. health inspectors this week visited an Enfamil baby formula factory run by Mead Johnson Nutrition Co as part of an investigation into the cause of bacterial infections that killed one infant and sickened another, a company spokesman said on Wednesday.
The visit is standard procedure in such investigations by the U.S. Food and Drug Administration, said Mead Johnson spokesman Chris Perille. Mead Johnson's own tests have twice found no sign of the bacterium at issue, Cronobacter.
The first wave of results could come as early as Friday, but the full investigation is likely to continue for several weeks, health officials have said.
"Because Cronobacter is so commonly present throughout the environment, we expect they are looking at a large number of other possible sources -- water, clothing, bedding, preparation and use surfaces," said Mead Johnson spokesman Chris Perille.
"This is standard operating procedure for them, and we would expect that they have also had inspectors visit production facilities for various other products/items they are testing as part of this investigation," he added.
Officials at rival formula makers Abbott Laboratories Inc and Pfizer Inc said their facilities had not been visited by health inspectors.
Shares of Mead Johnson have fallen 11 percent since Wal-Mart Stores Inc and other retailers pulled a certain lot of 12.5-ounce cans of Enfamil Newborn from store shelves after the death of 10-day-old Avery Cornett in Missouri.
So far no link has been established between any formula and the death of Cornett, who tested positive for Cronobacter, a bacterium that has sometimes been linked to rare illnesses in newborns and has been found in milk-based powdered baby formula.
FDA inspectors went to a Mead Johnson factory in Zeeland, Michigan, where the product was manufactured, and a facility in Evansville, Indiana, where some records were kept, the company said.
The investigation, by the FDA and the Centers for Disease Control and Prevention, involves testing samples of the baby formula, distilled water and the environment to which both babies -- Cornett and one in Illinois -- were exposed.
Before Cornett died on December 18, he was exposed to Enfamil formula purchased at a Wal-Mart store in Missouri.
The Illinois baby, who is recovering, was exposed to a variety of formula types apart from powdered Enfamil, as well as other over-the-counter products, according to the FDA.
"We do not have evidence showing that the two infections are related, and the two cases occurring in the last month may represent nothing more than a coincidence," CDC spokeswoman Kate Levinson said in an email.
A third baby, who is less than a month old and lives in Oklahoma, was also confirmed with a Cronobacter infection on Tuesday. That baby, who is recovering after treatment, was not exposed to Enfamil formula, according to state health officials.
No federal investigation into the Oklahoma case has been launched. Such a probe would start with local authorities gathering samples for testing, which is not in the plans as the infection happened earlier in December, according to a state Department of Health spokesman.
Cronobacter infections are not regularly reported to the CDC, and the agency officials say they on average receive four to six reported cases a year.
Reporting By Martinne Geller in New York and Alina Sellyukh in Washington D.C.; Editing by Matthew Lewis and Steve Orlofsky