Buffy The Vampire Slayer star Sarah Michelle Gellar has paid tribute to Michelle Trachtenberg, saying she will "always love" the American actress.
Trachtenberg, also known for Gossip Girl, was confirmed dead at the age of 39 after emergency medical services arrived at One Columbus Place, New York, following a call at about 8am on Wednesday, the city's police department said.
Her death is not being treated as suspicious and police said a medical examiner will determine the cause of her death.
Trachtenberg joined the fifth season of Buffy The Vampire Slayer as supernatural fighter Buffy Summers’ (Gellar) sister Dawn Summers, who is created with magic as part of that series’ storyline.
Gellar wrote a message on Instagram, quoting a line from the musical episode Once More, With Feeling when Dawn tells Buffy the "hardest thing in this world, is to live in it", after the slayer has confessed that she is feeling depressed after being resurrected from heaven in season six.
Gellar said: "'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'."
She also shared images of her and Trachtenberg during the show and behind the scenes with the cast.
During the musical episode, Trachtenberg sang a duet What You Feel with a demon, and also was part of the songs Where Do We Go From Here?, and the end of Give Me Something To Sing About with Gellar.
Tributes have come flooding in from fellow Gossip Girl stars including Blake Lively as well as members of the cast of Buffy The Vampire Slayer, including actress Alyson Hannigan, who played the witch Willow Rosenberg, and James Marsters, who played British vampire Spike.
How I Met Your Mother actress Hannigan shared a series of photos of Trachtenberg including old pictures from when they shared scenes.
Emma Caulfield, who played Anya Jenkins on the hit supernatural drama, said the cast had "lost a little sister" in a post shared to her Instagram story where she referred to Trachtenberg as "Mish Mish".
She wrote: "I'm so sorry your bright light died so young. Our Buffy family lost a little sister today.
"Rest in peace lovely Mish Mish. You were loved."
She said: "I am deeply saddened by the news of Michelle’s passing.
"She brought a loving energy to the set of Buffy. My thoughts are with Michelle’s family and friends."
Another co-star, actor David Boreanaz, posted a black and white picture of Trachtenberg to his Instagram story and wrote "So very sad. Horrible news."
Trachtenberg's character Dawn was romantically linked to Angel, portrayed by Boreanaz.
Elsewhere, James Marsters, who played British vampire Spike, said Trachtenberg was "a beautiful soul" as he shared a selfie of the two together on Instagram.
"My heart is heavy today. We have lost a beautiful soul", he said.
"Michelle was fiercely intelligent, howlingly funny, and a very talented person. She died much too young and leaves behind scores of people who knew and loved her.
"My heart goes out to her family who are good people and are suffering the greatest loss anyone could bear.
"I hope everyone can give them space to heal in this most difficult time. Godspeed Michelle. You are missed."
Source: Press Association
