Hayden Panettiere and Wladimir Klitschko had a daughter together in 2014
Hayden Panettiere's ex-partner Wladimir Klitschko has posted an emotional tribute to the "talented" late Heroes and Nashville star, who he said has "left this world too soon".
The former world heavyweight boxing champion, who shares an 11-year-old daughter with Panettiere, said the family is going through "profound shock and grief" following her death at the age of 36.
Panettiere died in Greenville, South Carolina, on Sunday and police said there were not "any signs of foul play or suspicious circumstances".
She had struggled for years with substance abuse and audio from police dispatchers and crews said they were responding to a "cardiac arrest" and detailed their efforts to resuscitate the woman after a possible "overdose".
The Greenville County Coroner's Office said crews treated a woman in "cardiac arrest" and her autopsy showed "no signs of trauma", but that the cause of death has not been confirmed.
Klitschko posted, external that the announcement of Panettiere's "tragic death saddens me deeply".
"She left this world far too soon. Hayden was, although no longer my partner, an important part of my life and the mother of our daughter, Kaya.
"She built an incredible career through immense talent, while also facing the darker sides of a very demanding industry. Nothing will erase the times we shared or the place she had in our lives."
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The pair, who met in around 2009, announced their engagement in 2013 and had their daughter together the following year. They never married.
"To our daughter Kaya, I will always speak of her mother with respect and make sure she remembers the person she was," he continued.
"I extend my deepest condolences to Hayden's parents, her friends, and her fans, who are also grieving today. Young and talented people like Hayden should not leave this world so soon.