Fairfield police arrested a woman on manslaughter charges Thursday in connection with the death of a 4-month-old Shelton boy at what they say is an unlicensed day care facility.

Police say they had probable cause to arrest Carol Cardillo, 53, in the March death of Adam Seagull after receiving autopsy results.

Investigators say it first appeared the baby died from sudden infant death syndrome. But the state medical examiner later found high levels of diphenhydramine -- the active ingredient in Benadryl -- in the infant's system. And police say Cardillo had much more of the drug.

"During the course of the investigation, detectives uncovered that the suspect had purchased 90 bottles of product with the chemical diphenhydramine," says Lt. Robert Kalamara, of the Fairfield Police Department.

The baby's parents say it was like losing their son all over again when they learned of the medical examiner's findings.

"The feeling that you have losing a child is one that I almost can't put into words, and I wish upon nobody," says Michelle Seagull, Adam's mother. "It's almost as if a part of us has been taken away from us."

Cardillo was later released on $250,000 bond. She was given a date next week in Bridgeport Superior Court. The day care has already been forced to close.