Hayden Panettiere's ex-fiancé Wladimir Klitschko has spoken out for the first time since the star's death.

The actress, who passed away on Sunday, had her daughter with the boxer, 50. In 2018, when Kaya was three, she signed full custody to her ex amid her battle with postpartum depression and addiction and Wladimir moved their daughter to his native Ukraine.

A post-mortem examination showed there were 'no signs of trauma' - although her official cause of death, which came less than a week before her 37th birthday, is yet to be confirmed. 

It was revealed on Monday that Narcan, a nasal spray used to rapidly reverse the effects of an opioid overdose, was found on a mattress in a loft apartment where Hayden died.

Naloxone, the active ingredient in Narcan Nasal Spray, blocks opioids like heroin, fentanyl, morphine and prescription painkillers from binding to brain receptors.

It allows the person to start breathing again within two to three minutes and stays active in the body for 30 to 90 minutes.

It is still unclear if Narcan had been used to try and revive Panettiere, although 911 audio obtained earlier on Monday revealed that the actress had gone into cardiac arrest following a suspected overdose.

Sharing a sweet snap of the family in happier times this morning, Wladimir wrote: 'Our family is going through a time of profound shock and grief...

'The announcement of Hayden’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...

'To our daughter Kaya, I will always speak of her mother with respect and make sure she remembers the person she was...

'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...

'I ask everyone to please respect our family’s feelings and privacy during this incredibly difficult time. For now, this is all I wish to say...

'Thank you to everyone who is supporting my family and expressing their sincere condolences...

'Rest easy, Hayden. May you find eternal peace.'

Hayden and Wladimir met at a book launch in 2009. After two years of dating, they split up in 2011, before rekindling their relationship two years later. 

In October 2013, they were engaged, with the actress giving birth to their daughter, Kaya, the following December. However, it was confirmed in 2018 that the couple had split again but remained on amicable terms. 

Later that year, Hayden announced she had made the 'difficult decision' to sign full custody of Kaya to Wladimir.

The widely-discussed move came after Hayden fell into a deep depression – which she said made her 'feel nothing' – and led to her 'turning to wine' and ultimately being sent to rehab for both depression and substance abuse. 

In her final interview in May, she spoke to Dear Mome about her choice, saying: 'It wasn't a decision I made lightly, nor was it a decision I even wanted to make. I was going through a really challenging time in my life.' 

She told Jay Shetty on his On Purpose podcast in May: 'I have been the one who sought it out, who was saying, "I desperately need help. I know this is going to look terrible, but I am. I cannot live like this anymore..."

'The idea that anybody would think that I would just give away my child and be OK with it is heartbreaking. It couldn’t be further from the truth...

'It became this horrible cycle for years of battling depression and anxiety and alcoholism and substance abuse, and just me trying to find my way back.'

She added: 'I love my daughter, and I'm so proud of the young woman she is becoming. I talk to her all the time, and I feel so connected to her. She's like a mini-me.'

Discussing the prospect of bringing her daughter back, Hayden insisted that she would not want to take her away from her 'incredible' life in Ukraine.

She said, 'By the time I finally got healthy, I felt like it would have been unfair of me to, and selfish of me to try to pull her out of this life that she had been creating.'

The star began acting as a child, appearing in soap operas then gaining wider recognition for her role in the 2000 sports drama Remember the Titans with Denzel Washington, and as the voice of Dot in Pixar's 1998 film A Bug's Life.

Hayden later found fame playing cheerleader Claire Bennet in the superhero drama Heroes before starring as country singer Juliette Barnes for six seasons on Nashville.

She earned two Golden Globe nominations for best supporting actress on the show, while her singing produced 11 entries on the US Billboard Hot Country Songs charts.

Hayden's film credits include 2006's Bring It On: All or Nothing, the comedy-drama film Raising Helen, and appearances in Scream 4 and Scream VI as Kirby Reed.

On Monday, Greenville County Sheriff's Office said that the post-mortem had been completed and that no signs of trauma were found on the star's body.

Further investigations will now take place to establish her cause of death, with chief deputy coroner Shelton England telling the Daily Mail that it was too early to discuss the drug overdose theory.

Meanwhile, a neighbor has spoken of the chaos that unfolded at the scene Sunday after Panettiere was found unresponsive and efforts to revive her proved unsuccessful.

Micah Lee, who lives in the Judson Mill Lofts complex where Panettiere died, claimed there was a 'bunch of commotion in the hallway' after the star allegedly 'collapsed' in a unit in the building.

'The halls are pretty hollow, so noise echoes throughout. And I had just heard about someone collapsing,' Lee told WYFF. 'And then afterwards there was talk about cardiac arrest. I can't confirm any of that. That's just what I've heard.'

In an audio of a 911 call made at 1.51pm Sunday, a female dispatcher described the actress as suffering a 'cardiac arrest.' A few moments later, a male dispatcher could be heard saying that she had suffered a suspected overdose at the home.

Hayden and her real estate agent ex-boyfriend Brian Hickerson were said to have flown from Los Angeles to South Carolina one day before she died.

Brian is originally from Greenville, public records show. It is unclear if the couple were in town to visit his family.

Her Nashville co-star Charles Esten also performed at The Foundry, a music venue inside the complex, on Friday night as part of his Carolina Tour.

Judson Mill Lofts is a former textile mill dating back to 1912, which was recently converted into apartments. These include studios and three-bedroom homes that can be rented from $1,295 to $3,485 a month.

Earlier, a representative for Hayden confirmed her death, saying her family would remember her as an 'incredible light' who brought 'immeasurable love and joy to all who knew her'.

A statement from her father, Skip, read: 'It is with profound sadness that we share the tragic passing of our beloved Hayden.

'She was an incredible light and a force of nature who brought immeasurable love and joy to all who knew her - and to the millions who watched her onscreen.'

Her father also asked that her family be given privacy as they 'take time to process this unimaginable loss'.