The mother was extradited to Deniliquin on Friday after appearing in Bendigo Magistrates’ Court by video link from Echuca, where police detailed her admissions to the alleged attempted drowning at Moama.

The older son, aged 9, remains in a serious condition at the Royal Children’s Hospital in Melbourne, and the younger son, aged 5, is missing, feared drowned.

Lawyers acting for the grandparents released a statement and a letter sent to the Albury Community Corrections Office on Thursday, claiming they “failed to act”.

“We had made considerable representations to Family and Children Services and the Department of Correctional Services about the imminent risk posed to the little boys with their mother’s release from prison,” the statement read. 

“Both departments failed to act and consequently we now have a grieving family.”

The letter claimed the mother was released to the grandparents’ house after she was released from prison in February, despite an apprehended violence order.

“Without any communication by your office (or police) or agreement from our client, (she) was released from jail... and taken to our client’s home with no regard for the AVO in place protecting our client,” it read.

“Further our client did not want her daughter to be living at the property since she was a victim of her daughter’s conduct over many years. 

“However, no permission or communication was afforded to our client about her daughter’s arrival.

“We advise that the daughter has now snatched the grandchildren and taken our client’s motor vehicle interstate.”

The woman sobbed as Detective Sergeant Trent Swinton read out the details of the incident to the court.

He said the mother arrived at a property on Perricoota Road – adjacent to the river – in the mid to late afternoon on Thursday with her two sons, aged 9 and 5.

Police allege she told her eldest son to get in the water before she attempted to drown him.

Detective Sergeant Swinton told the court the younger son was screaming during the incident.

The woman allegedly turned to the younger son, while the older son managed to struggle free before he was attacked by a dog.

She then allegedly attempted to drown the younger son, who was last seen drifting face-down in the water.

The older son was “savagely mauled” by the dog and was airlifted to the Royal Children's Hospital. Screams were heard by people on the riverbank who did not witness the incident.

Detective Sergeant Swinton said the woman made full admissions to her role in the incident, and told police of her "intention to kill both children".

The court also heard she allegedly told witnesses the night before that she “had to drown my babies”.

She will appear in the Deniliquin Local Court on Saturday.