She is still listed as a missing person case because investigators have yet to find her body.
Salt Lake County District Attorney Sim Gill said in an AP interview that the case is being handled as a murder investigation. While he wouldn't discuss the evidence, Gill said authorities don't have enough information to file charges in the case.
Her husband, Josh Powell, set his house on fire and killed himself and his two sons this weekend. He left a message for relatives apologizing, saying he couldn't live without his sons and didn't want to go on anymore.The recordings were obtained exclusively by ABC News.
"Hello, this is Josh. And I'm calling to say goodbye," Josh Powell was heard saying in the voicemail, which was played Tuesday on "Good Morning America."
Josh Powell, who was a person of interest in his wife's 2009 disappearance, died with his boys on Sunday. Before the fire killed them, investigators say he attacked his 5- and 7-year-old sons. According to an autopsy, the children suffered hatchet wounds to their necks.
The voicemail was left for Josh Powell's brother and other family members about 20 minutes before his house exploded in flames.
"I am not able to live without my sons, and I am not able to go on anymore," Josh Powell was heard saying. "I'm sorry to everyone I've hurt. Goodbye."
Josh Powell's boys, Charles and Braden, were at the house for a routine supervised visit. When they arrived, they ran ahead, while the social worker fell behind. The social worker stood outside pounding on the locked door, as Powell used a hatchet on his kids and lit the house on fire.
It seemed as if the boys had recently begun remembering details about their mother's disappearance.
Josh Powell claimed that the night his wife vanished in December 2009, he took the boys from their West Valley City home, about 10 miles outside Salt Lake City, on a midnight camping trip in freezing temperatures - a story her parents never believed.
Susan Powell's father, Charles Cox, said that the summer after his daughter disappeared, Braden drew a picture at day care of a van with three people in it, and told caregivers who asked him about it that it was a picture of his family going camping.
"Mommy's in the trunk," the boy reportedly said.
Authorities have not yet found Susan Powell. Josh Powell remained insistent to the end that he was not involved in his wife's disappearance.
In a motion seeking custody of his children, Powell said he missed his wife, and would remain strong for the boys.
"A lesser person would fall under the intense scrutiny I am facing, but apparently my inherent resilience as a person makes it increasingly difficult for them to pursue their agendas," Powell wrote. "I am standing tall for my sons, but it deeply hurts to face such ridicule and abuse.
The Associated Press contributed to this report.