PORTSMOUTH, N.H. (AP) – A couple whose day-old baby was given to the wrong mother to nurse in a hospital is demanding answers about how it happened.

The baby girl now must be tested for hepatitis C and HIV because there is a slight chance those diseases can be transmitted through breast milk.

“I want to know exactly how this error occurred,” the father told the Portsmouth Herald, which did not identify him.

Portsmouth Regional Hospital said in a statement that it is investigating and regrets the mixup, which occurred late last month. Hospital spokeswoman Nancy Notis declined to comment further Monday.

The couple also is frustrated because the mother who got their baby has a mixed-race infant and had misgivings when she got theirs, but didn’t speak up. The hospital arranged for the couples to meet.

“We point-blank asked her, ‘Did you not know you were taking care of our baby?’ and her response was ‘I thought it wasn’t my baby but I didn’t want to sound crazy so I didn’t say anything,”‘ the father told WMUR-TV.

He said the couple was told a nurse got the last digit wrong on the baby’s identification tag. But he said the nurse also should have made sure the names on the baby’s hospital ID matched that on the parents’.

“The ID card was on the bassinet,” the father said. “She did not follow protocol of looking at the cart, the ID number, room number, the baby’s race. All these things were missed by her.”

AP-ES-04-06-09 1212EDT