Cast members of "Buffy the Vampire Slayer," "Gossip Girl" and more are remembering their co-star Michelle Trachtenberg​ after the news of her death.

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

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