Michelle Trachtenberg, star of Gossip Girl, dies at 39

Michelle Trachtenberg, widely recognized for her roles in Buffy the Vampire Slayer and Gossip Girl, has passed away at the age of 39.

The actress was discovered unresponsive in her New York City apartment near Columbus Circle on Wednesday morning. According to police sources who spoke with ABC News, her mother found her.

Reports indicate that Trachtenberg had recently undergone a liver transplant and may have been dealing with post-surgical complications. Authorities believe she died of natural causes, and no foul play is suspected. The city's medical examiner will conduct an autopsy to determine the official cause of death.

Born and raised in New York City, Trachtenberg began acting as a child, landing early roles in Nickelodeon projects such as The Adventures of Pete & Pete and Harriet the Spy, the latter being her breakout film role.

She gained widespread recognition in 2000 when she joined the cast of Buffy the Vampire Slayer as Dawn Summers, the younger sister of Sarah Michelle Gellar's character. Her performance earned her a Teen Choice Award nomination for choice TV sidekick in 2001.

From 2008 to 2012, Trachtenberg played the cunning Georgina Sparks on Gossip Girl, a role that cemented her status as a fan-favorite antagonist. She was nominated for choice TV villain at the 2012 Teen Choice Awards for her performance.