According to press reports, two newborn girls born at Doctors Medical Center in Modesto, Calif. have contracted salmonella poisoning within three weeks of each other, prompting an inquiry into the matter.

Salmonella poisoning or salmonellaosis is a bacterial infection that causes diarrhea, fever and cramps for 12 to 72 hours after infection, but the illness lasts four to seven days, according to the Centers of Disease Control and Prevention. While most people recover, young children, elderly and immunocompromised individuals can have severe infections. About 400 people die each year with acute salmonellosis.

Sheila Vega, the mother of one of the girls – Skylin – asked for authorities to look into the matter. She told the Modesto Bee that the illness could cause permanent damage to her child, and she is still not safe because she is still is testing positive for the bacteria. Skylin was first diagnosed on April 19 after a stool test came back positive. She had been staying in the neonatal intensive care unit because she was born six weeks premature.

Sheila believes her daughter was poisoned by the formula the hospital gave her. Since Sheila took blood pressure medication during her pregnancy, the doctors gave Skylin pre-mixed formula as a precaution. Walker disputed those claims to the Modesto Bee, adding the state hasn’t said if it was related to a commercial product.

Abbott Laboratories, the maker of the Similac formula used at the hospital, said Tuesday that there’s no evidence formula caused the illness to the Modesto Bee.