Cases of infant botulism linked to formula have now been reported across 18 states, federal health officials said on Dec. 3.

Some 39 infants with confirmed exposure to infant formula made by ByHeart Whole Nutrition and suspected or confirmed cases of infant botulism have been recorded as of Wednesday, the Food and Drug Administration and the Centers for Disease Control and Prevention said in statements. The cases have been reported in 18 states.

That’s up from 37 cases in 17 states as of late November.

All of the infants have been hospitalized, some for weeks, although no deaths have been reported, officials said. The infants range in age from 16 days to 264 days, and illnesses started on dates ranging from Aug. 9 to Nov. 19.

States with cases are Arizona, California, Idaho, Illinois, Kentucky, Massachusetts, Maine, Michigan, Minnesota, North Carolina, New Jersey, Oregon, Pennsylvania, Rhode Island, Texas, Virginia, Washington, and Wisconsin.

Virginia is the latest state to report cases. The states with the most reported cases are Texas and California.

ByHeart products are sold online and in retail stores, including Walmart. Officials said that despite a recall of all ByHeart products, they’re still receiving reports that the formula is available on store shelves. They said they are working on immediately having the products removed from circulation and have urged people with formula at home to safely store it because if their child develops symptoms of botulism, which include loss of head control and difficulty swallowing, health officials may want to collect the formula for testing.

If children do not develop symptoms after 30 days, people should discard the formula, the FDA said.

If babies develop infant botulism, parents are urged to seek medical care for them. BabyBIG is the recommended treatment for the illness.

The FDA and CDC said they are investigating the multistate outbreak with the help of state officials and other partners.

Data from epidemiologic work and laboratory testing show that the formula from ByHeart “might be contaminated” with the bacteria that cause botulism, officials said on Wednesday. Additional testing is taking place.

ByHeart said on Nov. 19 that it tested 36 samples of formula across three lots and that five of the samples tested positive for the bacteria, Clostridium botulinum. The company said in late November that all lots of its formula may be contaminated.

“We continue to be focused on finding the root cause, through a rigorous audit of every step of our product development chain, from suppliers and raw ingredients, through to packaging and transportation,” the company said. “This includes testing more product samples.”

It is offering refunds for all products purchased on its website on or after Aug. 1.