Michelle Trachtenberg’s cause of death has been revealed one day after she died at 39 years old.

The Buffy the Vampire Slayer alum’s cause and manner of death were both officially listed as “undetermined,” the New York Medical Examiner’s office confirmed to In Touch on February 27, 2025.

A source told the New York Post that the cause of death was listed this way after her family reportedly objected to an autopsy. The medical examiner’s office was “obligated to honor the family’s request due to the state’s public health law,” according to the insider. Only an external examination of the body could be completed.

Insiders initially told ABC News on the day of Michelle’s passing that an autopsy would be completed to determine her cause and manner of death. A van from the NYC medical examiner’s office was photographed outside the Ice Princess star’s Manhattan apartment building on February 26, 2025.

Michelle was found dead in her New York City apartment on February 26, 2025, In Touch confirmed.

“On Wednesday, February 26, 2025, at approximately 0801 hours, police responded to a 911 call of an aided individual at 1 Columbus Place, within the confines of the Midtown North Precinct,” a spokesperson for the Deputy Commissioner of Public Information for the New York Police Department said to In Touch in a statement. “Upon arrival, officers observed a 39-year-old female unconscious and unresponsive. EMS responded to the location and pronounced the victim deceased.”

The victim was then identified as Michelle. Her death is not being investigated as suspicious.

Sources told multiple outlets after Michelle’s death that she recently underwent a liver transplant, noting that complications from the surgery may have contributed to her death. An insider told The New York Post that the Harriet the Spy actress’ body may have rejected the organ.

, a friend of Michelle’s, remembered the Gossip Girl alum in an Instagram post hours after her death and admitted that Michelle knew “death was a high possibility.”

“Sweetheart Michelle. What sad news this morning to wake up to. It feels weird and awful to be posting this, but I want to acknowledge your death because I cared about you,” she wrote. “I will always remember you as the young vivacious woman I met when I took this photo of you …”

The woman has since edited her caption, as it previously shared details about Michelle’s recent hospitalization. However, the original caption was shared by People.

“Seeing your face from the hospital bed when we FaceTimed recently, even though you did not look like you, your sweetness and humor were still alive,” the caption read. “I will not share the details of our conversations over the last six months. But you knew that death was a high possibility.”

The photographer wished for Michelle to have a “peaceful transition” and added, “I am only sorry that the outcome was not a better one.”