HARTFORD — An investigation of nine child deaths at Connecticut day cares found most of the victims died at illegal home care programs, raising concerns about the ability of low-income families to afford high-quality, legal child care, according to a new report released Tuesday.

The report by state Child Advocate Sarah Eagan's office examined child deaths in licensed and unlicensed home care settings between March 2016 and November 2017. There were no deaths at day cares that are not run in people's homes.

Six of the nine children died in illegal home day care programs. One of the six, a 4-month-old boy, died of a Benadryl overdose in March 2016, and the lead caregiver, Carol Cardillo, of Fairfield, was sentenced to 30 months in prison after pleading no contest to manslaughter.

Three other children cared for at unlicensed homes died natural deaths from medical problems, another died from head injuries after falling down stairs, and the cause of the sixth child's death remains unexplained.

Two of the three children who died in licensed home day care centers died while sleeping, and the causes of their deaths remain undetermined. The third child, a 2-month-old girl, died of blunt force trauma at a Stamford home day care in July 2016, and the operator, Nydia Carrillo-Maldonado, awaits trial on charges of manslaughter and risk of injury to a child. She has pleaded not guilty.

"There is nothing more heartbreaking than the death of a young child," David Wilkinson, commissioner of the state Office of Early Childhood, said in a statement.

"We are taking action to prevent these tragedies," he said. "Safety of our children is our highest priority. First and foremost that means getting them into safe, licensed care. We have made expanding access to care for infants and toddlers our highest priority and our plan we are now launching has been cited as a national model."

The child advocate's report recommends improving access to legal, high-quality day care for low-income families and strengthening efforts to ensure safe sleeping environments for children, through new licensing standards.

The report says children younger than 1 remain at the greatest risk for preventable death from unsafe sleeping environments.