ByHeart voluntarily recalled two batches of formula on November 8, but said the decision “was made purely out of caution, to go above and beyond what’s required and ensure the highest level of safety.”

On November 10, the company pressed the FDA to test unopened cans of its formula, suggesting that CDPH’s positive finding was due to contamination.

Things have changed since then. On Wednesday, the company said that it had partnered with an independent food-testing company, and the results were in: “We have just learned that those tests identified Clostridium botulinum in some samples of ByHeart formula.”

The company recommends that parents immediately stop using its formula products, all of which have been recalled. “ByHeart has grown because parents trusted us, and we are committed to rebuilding your trust,” it said.

The company also acknowledged that it has expanded the list of potential contaminants for its formula: “Until now, this bacterium was not among the pathogens routinely tested for across the industry,” ByHeart wrote. It emphasized that it is now cooperating with the FDA and working with others to figure out how its formula became contaminated.

The FDA said it is still testing the products and investigating the outbreak.