CHARLOTTESVILLE, Virginia (CNN) -- Police were investigating Friday whether two newborn girls were intentionally switched shortly after birth three years ago at the University of Virginia Medical Center.

The switch was revealed after one of the girls underwent three genetic tests earlier this month. DNA results proved that blue-eyed, blond-haired girl, whom 30-year-old Paula Johnson has loved and raised since bringing her home from the hospital, is not her biological child.

University officials have notified the other family involved and tests indicate that they, too, are raising someone else's child. Because of hospital confidentially rules, the other family's name has not been released.

The hospital insists safeguards it had in place would have prevented accidental misidentification after the June 1995 births.

The Associated Press and Reuters contributed to this report.

"Someone Else's Son" by Alan A. Winter "Garden of Lies" by Eileen Goudge "Daybreak" by Belva Plain Click here for additional reading on Switched at Birth