Prosecutors said Wednesday they have opened a criminal investigation against an employee of a German company that made a kosher baby formula (searchlinked by Israeli authorities to two infant deaths.

The company, Humana Milchunion (search), said Tuesday that an error in developing the formula left the soy-based milk substitute with less than one-tenth of the advertised quantity of Vitamin B1, which is vital for the development of babies' central nervous system.

Humana made Remedia Super Soya 1 formula for the Israeli firm Remedia, which is partly owned by American food giant H.J. Heinz Co. (search). 

Prosecutors in the western German city of Bielefeld are investigating a Humana employee on suspicion of negligent homicide and may extend the probe to others, spokesman Harald Krahmueller said. The employee was not identified.

Krahmueller said prosecutors don't know yet whether there is a connection between the two babies' deaths and the lack of Vitamin B1 (searchin the formula.

Israeli Health Ministry officials say more than 20 infants suffered from a disorder caused by a deficiency in the vitamin after drinking the formula, and two died.

The ministry recalled the product Friday and said its own tests showed a lack of the vitamin. Hundreds of parents whose babies were fed the formula flooded Israeli hospitals and medical clinics over the weekend to have their children examined.

Vitamin B1, also known as thiamin, is vital for development of the nervous system in babies.

On Tuesday, Humana said a content analysis of two previous versions of the product was misinterpreted in drawing up the new formula last February -- leading to the conclusion that no further Vitamin B1 needed to be added.

In addition, tests on a sample of the new product's first batch, taken March 21, were insufficient, Humana said.

Humana manager Albert Grosse Frie said the error was the result of a "unique combination of unfortunate circumstances." Without elaborating, he also said Humana was in contact with judicial authorities and would "draw the necessary organizational and personnel conclusions."

Remedia acknowledged that it had sought changes in the formula but blamed Humana for the mistake. Still, the Health Ministry said only the distributor, Remedia, was responsible in Israel.