The mother was arrested and charged with manslaughter, a Class C Felony.
The other two siblings are now in the custody of Child Protective Services.
According to police, they had never received a call out to the apartment previously.
"The biggest thing we can takeaway is to reiterate to parents to make sure you keep an eye out on your children even if you step away for a minute, something devastating like this can happen," Spring Valley Police Department Detective Matthew Galli told the outlet.
"It can happen to anyone. And it's unfortunate this took place."