Juliette Lewis doesn't think Misty Upham committed suicide.

The 41-year-old star, who co-starred alongside her friend in 'August: Osage County,' has called on police to launch a murder investigation after the 32-year-old actress' body was found near a river in Seattle, Washington yesterday (16.10.14).

Paying tribute to the late star on Twitter, Juliette wrote: ''I cant sleep. Too much darkness. I feel so sad about Misty. I know she has more to say. And about how she died. #RIPMistyUpham''

She later tweeted: ''Misty told me about horrible violence she suffered on NA reservations She felt she coul be murdered! Bcuz she was vocal #ThisIsNOTaSUICIDE (sic)

''#RIPMistyUpham I am in shock and greif. I pray the police do a murder investigation. They're saying not 'foul play' when ofcourse it is (sic).''

Misty was last seen on October 5 near a relative's home in Auburn, Washington after returning to the Seattle area to help care for her father Charles Upham, who suffered a stroke last year.

After discovering his daughter had gone missing, Charles revealed that his daughter was upset and erratic and had stopped taking the medication for her anxiety and bipolar disorder.

Police Commander Steve Stocker recently said there was no evidence or information ''to believe there is foul play''.