At that stage police had not recovered the body of her missing son, which was discovered by divers near the border town of Moama at 11.35am on Saturday.
NSW Police is co-ordinating the search which "will continue until dark tomorrow", while Victoria Police is providing air support and search and rescue teams.
"He was so little, it was very bad, the whole thing has been terrible, and everyone here is devastated", one emergency services worker told the Riverine Herald.
"Not only for the community, the police, but especially the family." he said.
Police were called to Perricoota Road near the Murray River after a nine-year-old boy was found with what police said were "serious dog bite injuries".
The woman's older son, aged nine, was also mauled and was taken to hospital but authorities spent Friday searching the river for the younger boy but couldn't find him.
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Detective Sergeant Trent Swinton told the court the younger son, aged, was screaming during the incident.
The body of a five-year-old boy has been found in the Murray River.
She then allegedly attempted to drown the younger son, who was last seen drifting face-down in the water.
The court heard people on the riverbank who did not witness the incident heard screams.
Detective Sergeant Swinton of New South Wales police said the suspect admitted trying to kill both her boys and allegedly told of having to "drown her babies" to witnesses.
The woman didn't appear before Deniliquin Local Court as expected on Saturday after requesting to stay in the custody cells at Deniliquin police station.
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The woman, 27, from Deniliquin, sobbed uncontrollably as she faced Bendigo Magistrates Court via video link just after 4.30pm on Friday afternoon.
"She has apparently made admissions, according to police", he said.
A police source told Fairfax Media the boys had been with their mother for at least two days, travelling through Victoria.
"The dog is four years old and it's never attacked one person, has grown up with kids, and it's always been around kinds playing", one told the Herald Sun.
Her nine-year-old son is in a Melbourne hospital in a serious condition after undergoing surgery following a dog bite. "She's confused and she's upset", he told reporters.
The grandparents previous year took out an apprehended violence order against the woman, who underwent a mental health assessment after a decline in her mental state on Wednesday.
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Her photo was published in a local newspaper as part of an operation cracking down on wanted criminals.
Deniliquin commander Superintendent Paul Condon was unable to confirm what role the dog played in the night's events.
The 27-year-old woman, who remains unidentified due to legal reasons, was seen to tell onlookers "I had to drown my babies" after holding her two children under the water in the Murray River on the Victoria-New South Wales border.
Up to 30 police searched to no avail until darkness fell on Friday night in the hope the youngest boy would be found alive in the fast-flowing river.
We have had a brief conversation with the nine-year-old last night.
"It's a awful story, it's a sad story, it's a tragic story, not only for the community, the police, especially the family - it's just bad".
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