'Buffy the Vampire Slayer' & 'Gossip Girl' actress Michelle Trachtenberg dies aged 39

American actress Michelle Trachtenberg, who acted in television series like "Buffy the Vampire Slayer" and "Gossip Girl", has died.

She was 39.

Found unresponsive

According to CBS News, the New York Police Department (NYPD) responded to a call on Feb. 26 morning (U.S. time) from an apartment in Manhattan.

When the police arrived, they found the actress unconscious and unresponsive.

She was pronounced dead at the scene.

According to BBC, NYPD is currently going through investigations to identify the reason for her death.

They released a statement stating:

"Criminality is not suspected. The medical examiner will determine the cause of death. The investigation remains ongoing."

Acting roles

Trachtenberg began her acting career at a very young age.

According to The New York Times, Trachtenberg starred in a television commercial for Wisk laundry detergent at the age of three.

The actress also made regular appearances on the Nickelodeon sitcom "The Adventures of Pete & Pete" from 1994 to 1996.

In 2000, she acted in the fifth season of "Buffy the Vampire Slayer" as the younger sister of the main character Buffy Summers.

She also played Georgina Sparks in "Gossip Girl".

Co-stars grieve her passing

Co-stars have taken to social media to express their condolences.

American actress Blake Lively posted on Instagram a message sharing:

"She was electricity. You knew when she entered a room because the vibration changed. Everything she did, she did 200 per cent. She laughed the fullest at someone's joke, she faced authority head-on when she felt something was wrong, she cared deeply about her work, she was proud to be a part of this community and industry as painful as it could be sometimes, she was fiercely loyal to her friends and brave for those she loved, she was big and bold and distinctively herself."

Co-star Rosie O'Donnell also shared with CBS News that Trachtenberg's death was "heartbreaking."

O'Donnell said she had "loved her very much. She struggled the last few years. I wish I could have helped."

Top image from @michelletrachtenberg on Instagram