By Sandra Gonzalez, Brynn Gingras and Dan Heching, CNN

(CNN) — Michelle Trachtenberg, the actress who rose to fame as a child star with films like “Harriet the Spy” and went on to have memorable roles on TV shows including “Gossip Girl,” has died, according to the New York City police. She was 39.

Police responded to a 911 call on Wednesday just after 8 a.m. local time, and found a woman unconscious and unresponsive inside a Manhattan apartment. She was later identified as Trachtenberg, according to an NYPD spokesperson.

EMS responded to the location and pronounced the victim deceased.

“Criminality is not suspected,” the NYPD said in a statement, adding that the investigation remains ongoing. Trachtenberg’s official cause of death will come from the Medical Examiner’s office.

Earlier on Wednesday, an NYPD source told CNN that Trachtenberg reportedly had a recent medical issue and that her death appeared to be related to natural causes and not suspicious.

CNN has reached out to representatives for Trachtenberg for comment.

With her precocious demeanor and sharp comedic timing, Trachtenberg fit in naturally with the over-the-top humor that dominated Nickelodeon in the ’90s. She first gained attention with a role on “The Adventures of Pete & Pete” and went on to star in Nickelodeon’s first feature film, 1996’s “Harriet the Spy.” In the latter, she shared the screen with Rosie O’Donnell, young Gregory Smith and J. Smith-Cameron, who would go on to star in “Succession” and played her mother in the project.

In 2000, she landed the role of Dawn Summers on The WB hit series “Buffy the Vampire Slayer,” playing Buffy’s (Sarah Michelle Gellar) polarizing younger sister. She remained with the series until its conclusion in 2003.

From there, Trachtenberg went on to several other high-profile TV appearances, playing Celeste on “Six Feet Under” and guest starring on shows including “House,” “Law & Order: Criminal Intent” (a callback to her first-ever screen credit on “Law & Order” in 1991) and “Weeds.”

She most recently appeared in two episodes of Max’s “Gossip Girl” revival.

It is unclear what she was working on at the time of her death, but she was active on social media. In the past week, she posted photos from her previous red carpets and reflected on the fashion.

“A memory, a magical night in #newyork. I remember feeling like Cinderella,” she wrote on one post roughly a week ago. “Wishing everyone an ethereal weekend.”

This story is developing and will be updated with additional information.

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