"That 70's Show" actress Lisa Robin Kelly died on Thursday. 

According to E! News, the 43-year-old actress, passed away in a rehab facility from unknown causes. The actress reportedly died in her sleep.

Kelly's agent, Craig Wyckoff released the following statement to People:

"Unfortunately Lisa Robin Kelly passed away last evening. Lisa had voluntarily checked herself into a treatment facility early this week where she was battling the addiction problems that have plagued her these past few years. I spoke to her on Monday and she was hopeful and confident, looking forward to putting this part of her life behind her. Last night she lost the battle. Cause of death has not been issued yet and no death certificate has been issued either."

Prior to her untimely passing, Kelly, who previously struggled with addiction, checked herself into a treatment facility. 

Kelly is best known for playing Laurie Forman, the floozy older sister of the Topher Grace character, Eric Forman, on the hit Fox show, which aired from 1998-2006. The actress exited the series in 2003 and was replaced by Christina Moore for the show's sixth season. According to ABC News, she had a drinking problem around the time she left the show.

The actress has made headlines for her legal troubles. She was arrested June 23 on suspicion of drunken driving. Kelly and her husband, Robert Joseph Gilliam, were arrested last November in connection with a disturbance at their home in Mooresville, N.C., a suburb of Charlotte. She was also arrested for domestic abuse in April 2012.

Danny Masterson, who starred as Steven Hyde on "That '70's Show," tweeted after news broke of Kelly's death Wednesday.

Terrible,awful news. Brilliant on 70s.... See u next time LRK,kisses. RT @sdavis53: #RIPLisaRobinKelly aka Laurie Foreman

— danny masterson (@dannymasterson) August 15, 2013