MODESTO (CBS13) – Two newborn baby girls born at Doctors Medical Center in Modesto contracted salmonella poisoning in a three-week span.

The scariest part for expecting parents is that hospital administrators and county health officials have not been able to pinpoint how the infants, treated at the hospital, got the bacteria in their systems.

“We don’t have an answer yet. However, there has been intense investigation,” said Dr. John Walker, Stanislaus County Public Health.

One of the infant’s moms sparked the investigation.

She suspects salmonella-tainted formula given to her newborn, while in the neonatal intensive care, caused the illness.

In a statement, a hospital administrator says, “Doctors Medical Center takes this issue extremely seriously and after thorough review it appears that all hospital policies and protocols were followed. It appears that this was an isolated event.”

Walker says salmonella poisoning in newborns is extremely rare.

The biggest concern is if the infection would turn into an outbreak, which hasn’t happened.

“Fortunately this doesn’t appear to be a widespread issue; however, state Department of Health is looking closely and hopeful all of us get answers soon,” said Walker.

Health officials say the typical incubation period for salmonella is about a week and a half.

No other cases have been diagnosed within the time period.