Michelle Trachtenberg, known for roles in “Buffy,” “Harriet the Spy” and “Gossip Girl,” was found dead in a New York City apartment at the age of 39 in February, the NYPD said. The NYC Office of Chief Medical Examiner has now announced a cause of death for the actor.

Trachtenberg died of natural causes from complications of diabetes mellitus, the medical examiner’s office said. The medical examiner’s office said it was able to make the determination following laboratory tests.

The NYPD responded to a 911 call around 8 a.m. on Feb. 26 to a luxury apartment building in the Columbus Circle area, police said. When officers arrived they found Trachtenberg unconscious and unresponsive, according to the NYPD.

Police sources say Trachtenberg’s mother was the person who found her and called 911.

Trachtenberg was pronounced dead at the scene at One Columbus Place, on West 59th Street between Ninth and Tenth avenues, which sources said was her residence. At the time, authorities said criminality was not suspected in her death and it was not believed to be suspicious.

“The family requests privacy for their loss,” Trachtenberg’s representative, Gary Mantoosh, said in a statement at the time.

One of her most popular and longest roles, Trachtenberg received acclaim for her role as Dawn Summers on “Buffy the Vampire Slayer” in the early 2000s, alongside Sarah Michelle Gellar. She starred in a number of film and television roles throughout her career including “Harriet the Spy,” which was one of her first acting roles, and “Gossip Girl,” in which she played Georgina Sparks.

The creators and showrunners for “Buffy” said in a statement that Trachtenberg “was a delight to have on set and will be deeply missed. Our thoughts are with her family.”