Lisa Robin Kelly, who rose to fame as Laurie Forman on "That '70s Show" died on Wednesday night, her manager told FOX411. She was 43.

The actress died in a rehab facility, and her cause of death is still unknown.

"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," her manager Craig Wycoff said. "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."

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," he said.

Kelly portrayed Laurie Forman, sister of Topher Grace's lead character Eric, on the Fox series. It concluded in 2006.

Unlike some of her co-stars — Grace, Ashton Kutcher and Laura Prepon — Kelly fell out of the spotlight after appearing on the sitcom until she started making headlines for personal troubles.

Since Kelly's role on "That '70s Show" wrapped, she was often in the news for her legal battles. Most recently on June 23, the actress was arrested on suspicion of drunken driving.

It was not her first brush with the law. Kelly and her husband Robert Joseph Gilliam were arrested last November in connection to a disturbance at their home in the Charlotte, N.C., suburb of Mooresville.

The Associated Press contributed to this report.