Michelle Trachtenberg's cause of death was ruled "undetermined" by the Office of Chief Medical Examiner in New York City, Fox News Digital confirmed.

Michelle Trachtenberg’s former “Buffy the Vampire Slayer” costar Sarah Michelle Gellar is looking back at their time together on screen and off, one day after Trachtenberg died in New York City.

Michelle Trachtenberg's cause of death was revealed Thursday after the 39-year-old actress was found dead in New York City Wednesday morning.

The cause of death for actress Michelle Trachtenberg has been ruled “undetermined” by the New York City Medical Examiner, according to an agency spokesperson.

The cause and manner of Michelle Trachtenberg’s death are undetermined, according to the New York City Office of the Chief Medical Examiner.

Rosie O’Donnell paid tribute to her former co-star, Michelle Trachtenberg, who was found deadin her New York City apartment on Wednesday. “Heartbreaking,” O’Donnell said in a statement to Us Weekly. “I loved her very much.

Actress Michelle Trachtenberg has died at age 39. The beloved actress was found dead at her apartment in New York City on Wednesday, February 26. The New York Police Department confirmed to People that they responded to a 911 call at 1 Columbus Place around 8 a.

Eugenie became friends with Trachtenberg when she lived in New York City and worked for the art auction start-up Paddle8 from 2013 to 2015. Their friendship first became public in December 2013, when they were photographed courtside at a Knicks game alongside actor Michael K.

Shortly after Michelle Trachtenberg's death, legal expert Neama Rahmani tells PEOPLE why a family would decline an autopsy after the late actress' loved ones objected to the procedure being performed.

Michelle Trachtenberg was found deceased in her apartment; no foul play is suspected, with her recent liver transplant possibly a factor.

Michelle Trachtenberg was set to make a SXSW appearance in Austin in March before she died in New York City earlier this month