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.

Blake Lively on Wednesday shared a lengthy tribute to her “Gossip Girl” costar Michelle Trachtenberg, who was found dead in her New York City apartment on Wednesday morning. Trachtenberg, also known for her roles in “Buffy the Vampire Slayer” and “Harriet the Spy,

Trachtenberg's mother found her in her apartment near Columbus Circle in New York City. No foul play is suspected, according to sources. Trachtenberg's " Buffy the Vampire Slayer " co-star James Marsters took to Instagram and paid tribute to the actress with a moving message and a photo of the both of them.

Actress Michelle Trachtenberg, known for her role in "Gossip Girl," was found dead in a New York City luxury apartment building by the NYPD. She was 39.

Michelle Trachtenberg was found in her New York City apartment, and the death is not believed to be suspicious, police said.

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.

Former child star and beloved millennial actor Michelle Trachtenberg, best known for her roles in "Buffy the Vampire Slayer" and "Gossip Girl," has died at 39 years old. The New York Medical Examiner is investigating the cause of death.

Michelle Trachtenberg, who rose to fame as a child star in the 1990s and 2000s, has died aged 39, the New York Police Department told CBS News, the BBC's US partner. The American actress was best known for playing Buffy the Vampire Slayer's younger sister Dawn Summers,

Michelle Trachtenberg, star of “Buffy the Vampire Slayer” and “Harriet the Spy,” has died at age 39, according to the New York Police Department. The cause of death was not immediately disclosed, but her death was not believed to be suspicious,