Mikayla Miller was found dead by a jogger in a wooded area near her apartment in Hopkinton on the morning of April 18.
The Middlesex County District Attorney's Office announced the findings from the state's medical examiner in a statement Tuesday.
"Our investigation into the events surrounding Mikayla’s death remains active and ongoing,” the office wrote in a statement, according to The Associated Press.
“We will continue to explore every investigative angle necessary as we do that work and intend to issue a complete and thorough report at the conclusion of the investigation," the statement said.
The office did not immediately respond to a request for comment from NBC News Monday night.
Mikayla's mother, Calvina Strothers, has raised questions about the investigation into her daughter's death.
District Attorney Marian Ryan has defended the investigation and rejected any suggestion that her office neglected the case because Mikayla was Black and a member of the LGBTQ community. "That is painfully false," Ryan has said.
Strothers could not be reached for comment Monday night.
Strothers has said her daughter was jumped by five teenagers the day before she was found dead. She also has said she was told almost immediately that her daughter died by suicide, a conclusion she called premature and without a proper investigation.
Ryan's office has said that cellphone records from the night Mikayla was last seen showed she traveled 1,316 steps between 9 p.m. and 10 p.m., and those steps are "roughly the same distance from her home to the location where her body was found."
Her office said an investigation showed the teen was in an alleged physical altercation with two of four teens who were at a recreation room on April 17 and a fifth teen was outside in a car.
Her office said investigators were later able to confirm that the five were in other places the night Mikayla was last seen.
Ryan earlier this month pledged that once the investigation is over, and with permission of Mikayla's family, she would "release every shred of legally releasable information."
If you or someone you know is in crisis, call the National Suicide Prevention Lifeline at 800-273-8255, text HOME to 741741 or visit SpeakingOfSuicide.com/resources for additional resources.