Sarah Michelle Gellar issues heartbreaking tribute to Michelle Trachtenberg after she died aged 39

Sarah Michelle Gellar has issued an emotional tribute to Michelle Trachtenberg who was found dead in a New York City apartment near Columbus Circle on Wednesday (26 February).

Authorities have said the 39-year-old's Gossip Girl star's death was not being treated as suspicious, with the NYPD adding that an autopsy will soon be conducted by the medical examiner's office to determine the cause of death.

A number of tributes have since flooded following news of Trachtenberg's death including one from Gellar, who she starred alongside in Buffy the Vampire Slayer.

Gellar captioned a series of photos uploaded to Instagram: "Michelle, listen to me. Listen. I love you. I will always love you. The hardest thing in this world, is to live in it. I will be brave. I will live… for you."

Ed Westwick, best known for playing Chuck Bass on Gossip Girl alongside Trachtenberg, has also taken to Instagram to pay tribute to the late star.

Writing on his story, the British actor said: "So sad to hear of the passing of @michelletrachtenberg sending prayers," accompanied with a prayer emoji and a white heart.

Blake Lively, who played Serena van der Woodsen on the show, has likewise taken to Instagram to share a heartfelt message to her beloved late co-star.

She captioned a photo of them on set taken from the 'first day' she ever met Trachtenberg, writing: "She was electricity. You knew when she entered a room because the vibration changed. Everything she did, she did 200%.

"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 distinctly herself."

Sharing a sweet anecdote from their days on the Gossip Girl set together, Lively continued: "And she always had yummy caramel smelling lipgloss on because she didn't just want to sparkle on camera, she liked creating a nice experience for anyone who was in her orbit, even down to the subtle smell of her lipgloss because she cared about the sweet details.

"She was a kind person, through and through."

Explaining that 'time passes', Lively went on to add: "You take for granted that you get the chance to see an old friend. To paraphrase, the real tragedies in life are the ones that blindside you on an idle Tuesday."

Issuing a piece of advice to her followers reading the tribute, the actress resolved: "Hold those you love and have loved dear. The world lost a deeply sensitive and good person in Michelle."

"May her work and her huge heart be remembered by those who were lucky enough to experience her fire," Lively concluded.