Fire would soon engulf the property and kill two young girls, a one-year-old and a five-year-old.
Their mother, Shania Lee, allegedly heard screaming as she watched home security cameras on her phone after leaving.
"Investigators believe that the referred screaming is in relation to children during the fire," Detective Senior Constable Chris Mitchell told Melbourne Magistrates Court on Wednesday.
"It's upsetting and an aggravating circumstance in relation to this offending ... exacerbated by the fact that Lee did not call triple zero to assist her own children."
Lee allegedly told co-accused Matthew Mcaulliffe about hearing screaming over a recorded prison phone call, he said.
In another recorded prison call, Lee allegedly said the fire was not her fault but "the only thing I could get f***ed up for" was leaving her kids alone.
"But it's not like I f***ing fully just left it, like I had a camera in the kitchen, so I can make sure they didn't get out of bed or anything like that," the detective claimed she told another man.
The shocking details about the deadly 2024 blaze were aired as Lee, 26, successfully applied for bail via video link.
She has been charged with two counts of negligent manslaughter and one of negligently cause serious injury.
Lee was seen leaving her Sydenham home, Melbourne's northwest, in a Jeep at 9.17pm on September 8, 2024, the detective said.
"At 9.18 and 47 seconds, a smoke alarm is activated before a child can be heard crying," Det Mitchell said.
The detective alleged she and Mcaulliffe left the children home alone to collect a second-hand car part together.
He said the fire started in the master bedroom and neighbours called out to see if anyone was inside the home but did not get a response.
Emergency services arrived at 9.39pm and found the children, alive but unconscious.
They were taken to hospital and the two young girls died three days later.
He said police had engaged an expert to examine possible causes for the fire, with the "most likely" to be ignition of a flammable material such as a box of clothing.
Det Mitchell said Mcaulliffe, who has passed a statement onto police, was a cigarette smoker who claimed he did not smoke inside the house.
He is believed to be the last person to enter the master bedroom before the fire, but Lee allegedly told police ignition from a cigarette was "unlikely".
Jemena Energy has examined potential electrical faults in the home but found no evidence of anything abnormal.
Det Mitchell and the prosecution opposed bail due to her risk to the safety and welfare of the community, and her prior offending, which included bail contraventions and avoidance of police.
She is also accused of burglary, weapons and theft offences, from December 2024, which she will contest at Werribee Magistrates Court.
Lee's lawyer Sam Norton said her risk was not unacceptable because he asked for her to be bailed to a NSW address.
He said there was no evidence Lee knew there was a fire in the home when she walked out the door, and that she was not charged with causing the fire.
"This case has got massive, massive issues," Mr Norton said, adding it could take two years for it to get to trial.
Det Mitchell said they were "trialable issues". He alleged the fire may have started before Lee left the home and she could have been aware due to radiating heat from the closed bedroom door.
Magistrate Michael Smith approved Lee's release on bail to Moama, NSW, with conditions that she reported to Echuca police in Victoria three days a week and notify police if she changes address.
She will return to the court on January 15.
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