CRIMINAL information may have been covered up by the failure to report the deaths of three children in state care, the State Coroner has found.

Coroner Mark Johns' annual report criticises Families SA for failing to report the deaths, as required for all children in state care.

"At worst, the opportunity to obtain evidence of possible wrongdoing has been lost," the report states. "In these cases, the coronial process has been compromised. The opportunity to carry out a post-mortem examination may have been lost.

"Certainly the opportunity to learn from the event, and to make recommendations that may prevent a recurrence, has been lost. These are matters that society should be concerned about."

The criticism relates to three disabled children identified only as JL who died in January aged 17, AO who died in July last year aged 12 months and ML aged 17. JL died of natural causes after suffering severe intellectual disability since birth, AO died after being born with a severe neuromuscular disorder and ML from pneumonia.

Under section 28 of the Coroners Act, failure to notify of the death of a child in state care is punishable by a maximum fine of $10,000 fine or imprisonment for two years.

On all three occasions the office of the Minister for Families and Communities was advised of the deaths, but the report blames departmental officers for not reporting the incidents to the Coroner's office.

A spokesman for the current Minister for Families and Communities, Jennifer Rankine, said the issue had been raised with the department. "I am advised that measures have been put in place to make sure the department notifies the Coroner of any such deaths," he said.

None of the fatalities were reported to police.

The Coroner's report stated: "The Department did not fulfil its obligations to report these deaths and has informed me that it has since developed appropriate policies and procedures . . ."