The “Buffy the Vampire Slayer” and “Gossip Girl” actress died in February at 39.

Michelle Trachtenberg’s official cause of death at 39 has been revealed.

The finding came after review of laboratory test results, and the manner of death was ruled as natural.

Michelle Trachtenberg on ‘Gossip Girl’

Michelle Trachtenberg on ‘Gossip Girl’.HBO

HBO

Trachtenberg’s passing prompted an outpouring of grief from fans and former castmates.

She struggled the last few years.

I wish I could have helped."

Chace Crawford, Michelle Trachtenberg, blake lively

I will always love you.

The hardest thing in this world, is to live in it.

I will be brave.

Actress Michelle Trachtenberg attends The Art of Elysium 2016 HEAVEN Gala presented by Vivienne Westwood & Andreas Kronthaler at 3LABS on January 9, 2016 in Culver City, California

John Shearer/Getty

I will live… for you."

Because they were the two best, by a landslide."