Tina Fontaine, 15, was in a vehicle pulled over by two officers more than a week after she was reported missing last summer, but she was not taken into custody. Her body was found nine days later in a bag in the Red River.
No arrests have been made in her death.
Both officers were put on administrative leave in October. The force says the other officer will remain on administrative leave pending the outcome of disciplinary proceedings.
Police have not said if their investigation determined whether the officers knew Tina's identity at the time, or whether they were aware she had been reported missing.
"At this time no further details will be provided as it is inappropriate to provide details of the regulatory investigation," police said in a release Tuesday.
But Thelma Favel, Tina's great-aunt, said the officers did know the girl was reported missing.
"My baby might still be alive today if they just did their job," Favel said Tuesday. "They did run her name through the system because I was told that by the chief investigator that they did run her name through, but they just let her go even though she was intoxicated.
"They should have just fired them on the spot."
Tina had spent much of her life with Favel, on the Sagkeeng First Nation, about 70 kilometres northeast of Winnipeg. She had a history of running away and went to Winnipeg about a month before her death to visit her biological mother.
Favel had asked a child welfare agency for help with Tina. The girl was supposed to be in a group home or foster home, but had run away and wasn't seen for more than a week when police made the traffic stop on Aug. 8.
Favel said social workers have told her that on that night — a few hours after police came across Tina — the girl was found passed out in an alley downtown. Paramedics took her to a nearby hospital.
Favel said Tina was kept for a few hours until she sobered up, then social workers picked her up at the hospital.
She ran away again and was found dead Aug. 17.
Police Chief Devon Clunis ordered an internal investigation into the officers' actions and it was forwarded to Manitoba Justice, which said it would not proceed with charges under either Criminal Code or the Child and Family Services Act.
Favel said she has little hope that Tina's killer will be found.
"I have a feeling that Tina's case will go unsolved, just like the rest of the murders of these aboriginal girls."
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