Lily Peters, a 10-year-old Wisconsin girl found dead after she vanished while visiting her aunt, died from blunt force trauma and strangulation, authorities confirmed Thursday.

The preliminary autopsy also determined the girl’s cause of death to be homicide. A final report is expected within 4-6 weeks after toxicology testing is complete, Chippewa County Coroner Ron Patten told The Post.

Lily, who was visiting her aunt just blocks away from her Chippewa Falls home, was “probably” assaulted with a “large tree branch” during the brutal attack, Patten said.

“There’s other damage to the body, but we’re not sure what caused that at this point,” Patten said, adding that the girl was likely assaulted with multiple items. “It’s all being processed at this time.”

Patten said he had no additional information to provide, but the findings jive with what prosecutors said in court Wednesday as a 14-year-old boy was charged in her gruesome slaying. The teen, identified in court solely by his initials, was ordered held on $1 million cash bond.

“He punched the victim in the stomach, knocked her to the ground, essentially strangled her, hit her with a stick, before strangling her to the point of death — before he then sexually assaulted her,” Chippewa County District Attorney Wade Newell said Wednesday.

The prosecutor had asked a judge to hold the accused teen killer on such hefty bond in part due to disturbing statements he made to police, indicating he was a threat to the small town of 14,000.

The teen, who was arrested Tuesday, told investigators he intended to “rape and kill the victim from the get-go,” Newell said.

Lily’s accused killer has been charged with first-degree intentional homicide, first-degree sexual assault and first-degree sexual assault of a child under the age of 13 resulting in great bodily harm.

The slain girl found dead Monday was a fourth-grader at Parkview Elementary School in Chippewa Falls, where students and staff throughout the district are being asked to wear purple Friday in her honor.