Wladimir Klitschko

Wladimir Klitschko has filed for guardianship of his 11-year-old daughter with the late Hayden Panettiere to protect her inheritance amid federal investigations and security concerns.

Authorities are investigating whether actress Hayden Panettiere died from an oxycodone pill laced with fentanyl. The 36-year-old star was found unresponsive in August.

Panettiere, who played cheerleader Claire Bennet in "Heroes" and starred in "Nashville," died just days before her 37th birthday. A representative confirmed her death, but at this stage, no details regarding the circumstances have been provided.