Gardaí are treating the deaths of a mother and her infant son in Dublin overnight as a family tragedy.

The post-mortem on the body of the seven-month-old boy has been completed this evening.

It is believed the results are inconclusive but gardaí said they are not releasing them for operational reasons.

The post-mortem on the child's mother, who was in her 30s, is expected to be carried out tomorrow.

Gardaí in Lucan are not looking for anyone else in connection with the deaths.

A file is expected to be submitted to the Coroner but criminal proceedings are not expected to be pursued.

Gardaí were called after the woman, who worked as a paediatric nurse, was seen behaving erratically at the M50 Toll Bridge at around 3.45am this morning.

Her body was subsequently found below the bridge at the Lower Road at the Strawberry Beds.

When it was recovered and identified, gardaí went to the woman's home in Lucan in Co Dublin where they discovered the body of her seven-month-old baby boy.

The house has been sealed off for a forensic examination.

The body of the child was removed for a post-mortem at the Children's Hospital in Crumlin. Gardaí said they are working to establish the facts but are not conducting a criminal investigation.

"The primary focus of the investigation team at this time is the preparation of an investigation file for the Coroner in respect of the still unexplained death of the infant boy," the statement said.

The coroner will ultimately determine the cause of the child's death which is suspicious but will not attribute blame to anyone.

An incident room has been established at Lucan Garda Station and the coroner's office has been informed.

The family of the mother and child have appealed for privacy.