Unravelling the mysterious disappearance and unsolved murder of Amber Tuccaro could hinge on identifying a man whose voice was captured in a recording of her last phone conversation, new details of which her family has revealed to CBC News.

Police released 61 seconds of audio, but CBC News has learned that the full audio recording is 17 minutes in length, which corresponds almost directly to the amount of time it would take to drive from the motel where Tuccaro was staying to the site where her body was found two years later.

The 20-year-old mother from the Mikisew Cree First Nation in Alberta vanished almost five years ago, after getting into an unknown man's vehicle in Nisku, near Edmonton. She was staying in the area for a few days after arriving from Fort McMurray with her infant son and a female friend.

And how many more women, girls are going to be killed before he's caught? - Tootsie Tuccaro, Amber's mother

Amber's case is now in the hands of RCMP's KARE, a unit based in Edmonton that is investigating unsolved homicides and cases of vulnerable missing persons. Her family has filed a complaint with RCMP's Civilian Review and Complaints Commission after the RCMP admitted mishandling the initial investigation into her disappearance.

In 2012, the RCMP released a disturbing audio recording in which Tuccaro is heard talking to the driver, saying, "You better not be taking me anywhere I don't want to go."

The man insists he's driving north, to "50th St.," and while Tuccaro repeats what he's telling her to the person on the other end of the phone, the call ends abruptly.

RCMP investigators believe that rather than driving Tuccaro north into the city, the man actually drove southeast along the rural roads of Leduc County.

Tootsie Tuccaro, Amber's mother, says someone must recognize who this man is. (CBC)

"I have a hard time listening to the recording," says Amber's mother, Tootsie Tuccaro. "My baby sounded so scared."

RCMP now says this was the only time in Canadian history it released an audio recording to the public in a homicide investigation.

On Sept. 1, 2012, just four days after its release, horseback riders found Tuccaro's partial skeletal remains in a farmer's field in Leduc.

According to RCMP spokesperson Mary Schlosser, the discovery of Tuccaro's remains so soon after the audio was released "is entirely coincidental."

"There's somebody out there that recognizes the voice. Has to be. His mom, his sister, his wife. And they're not coming forward? Do they not have a conscience?" asks Tuccaro's mother.

Source of call revealed

RCMP have refused to disclose how they got the recording or who Tuccaro was speaking to on her cellphone. But CBC News has learned that the call to Amber came from her brother, who was being held in the Edmonton Remand Centre at the time.

The centre began recording all outgoing calls by inmates earlier in 2010.

"Amber's case is about the voice, the man's voice, and now I'm Amber's voice." - Tootsie Tuccaro, Amber's mother

It's unclear why it took two years after Tuccaro's disappearance for the recording to be released, but her family tells CBC that several months before they were made aware of its existence, and before her remains were found, RCMP told them they believed Amber had been murdered.

"There's a lot of things we don't know. We have a lot of questions that we're not going to get answers to because it's an ongoing case, and even if the killer is found we'll probably never hear some of the whole story," says Tootsie Tuccaro.

The complaint filed with the RCMP's Civilian Review and Complaints Commission alleges that Leduc RCMP's mishandling of Tuccaro's disappearance hindered the subsequent homicide investigation.

"Even when I reported her missing they asked me if she ever went missing before. 'Oh, she's probably out partying and she's gonna come home, she'll call,'" Tuccaro says she was told by Leduc RCMP.

Members of the group, Stolen Sisters and Brothers Awareness movement, put up posters like this one near Leduc., hoping to get answers in the growing number of cases of missing and murdered aboriginal women. (Travis McEwan/CBC)

On Sept. 4, 2010, less than three weeks after Tuccaro's disappearance, a media relations officer with Leduc RCMP was quoted in a local newspaper saying, "We don't have any reason to believe she is any danger. We know that she is in the Edmonton area."

According to RCMP spokesperson Mary Schlosser, "the accuracy of this media comment is now under CRCC review."

Police also removed Tuccaro's name from its list of missing persons and, without informing her family, destroyed her belongings, which had been left at the motel in Nisku.

"Let's just say that's not best practice and something that shouldn't have happened but did," says Schlosser. The RCMP later apologized to Tuccaro's family.

Many unsolved cases in area

KARE investigates unsolved homicides and cases of vulnerable missing persons. And while the RCMP won't say how many cases KARE is investigating, CBC's Aboriginal Unit has found at least 15 unsolved cases of indigenous women who vanished or were murdered in and around the Edmonton area.

The partial remains of four of those women, including Amber Tuccaro, were all found within a few kilometres of each other in Leduc County.

I know that voice... There's no doubt in my mind that it's his voice. - Woman who says she recognizes the man's voice

The most recent discovery came this spring when the remains of Delores Brower were found on a rural property, more than 11 years after she disappeared.

"Maybe it`s the same guy that's killing these other women that are found in Leduc and Nisku area. And how many more women, girls are going to be killed before he`s caught?

"Because these people that know are not coming forward and identifying him," says Amber Tuccaro's mother.

Asked whether RCMP investigators believe one person could be responsible for multiple murders, Schlosser says: "That's a possibility that they certainly would be considering."

It's also a possibility that has people who live in the area on edge.

One woman contacted CBC News to say she's convinced she recognizes the man's voice heard on the audio recording released in Amber Tuccaro's case.

"I know that voice. I've ridden with that voice before on several occasions. There's no doubt in my mind that it's his voice," said the woman, whose identity CBC has agreed not to reveal.

She says she reported his name to the RCMP three years ago.

CBC News interviewed two other women who say they've reported the same man to police, suspecting it's his voice on the recording.

One of the women says she called the RCMP about her suspicions as recently as three months ago.

An RCMP investigator reached out to CBC News to say the Mounties have looked into the man, but have ruled him out as a person of interest in the Tuccaro investigation.

"They didn't look very hard I don't think," says one of the women, still convinced she knows the identity of the man on the recording.

"I knew the voice like I know the back of my own hand."

Tootsie Tuccaro visits her daughter's grave. (CBC)

Tootsie Tuccaro says she welcomes all tips in her daughter's case, and is convinced that as more people hear the recording, someone will come forward with information that will lead to an arrest.

Until that happens, Tuccaro is maintaining a ritual, posting the audio recording on social media every day, imploring the public to help catch her daughter's killer.

"I think about the voice all the time," she says.

"It's kind of messed up because Amber's case is about the voice, the man's voice, and now I'm Amber's voice."

CBC continues to investigate the stories of missing and murdered indigenous women and girls. If you know anything about this case, or any other unsolved MMIW case, email us at MMIW@cbc.ca.