Lisa Robin Kelly Dead At 43: 'That 70s Show' Actress Dies 2 Days After Checking Into Rehab; How Did She Die? [VIDEO]

Lisa Robin Kelly, best known for her role as Laurie Forman of "That 70s Show," had allegedly been staying at a rehab facility for the past week. She died in her sleep Wednesday at the facility for reasons that are still unknown. She was 43. The actress had been open in the past about her substance abuse problems, which began while she was still working on the set of "That 70s Show."

She checked in to the rehab facility of her own will. She spoke to her agent, Craig Wyckoff, Monday and appeared to be doing well, he told reporters. He said she was optimistic and seemed eager to put her abuse problems behind her.

"I spoke to her on Monday and she was hopeful and confident, looking forward to putting this part of her life behind her," Wyckoff said. "Last night she lost the battle. Cause of death has not been issued yet and no death certificate has been issued either."

Kelly got her start in an episode of "Married...With Children" in 1992 and made several small appearances in major shows such as "Charmed" and "Murphy Brown" in the 90s. She got her big break playing the sister of main character Eric Forman, played by Topher Grace, in "That 70s Show," who was often seen with her sights on character Kelso, played by Ashton Kutcher, who was in a relationship on the show. She was replaced by Christina Moore when she left the show after five years. She eventually opened up about her decision to leave, citing addiction and personal tragedies.

"I had lost a baby," Kelly said. "As a result of that I lost it. I lost everything and I was abusing alcohol. With 'That '70s Show' I was guilty of a drinking problem, and I ran."

Kelly had been arrested several times after quitting the show. She pled guilty to misdemeanor drunken driving in 2010 and served a night in jail and was given one year of unsupervised parole. She was arrested in March 2012 on one count of spousal abuse, a charge that was later dropped. In November of the same year, both she and husband Gilliam Kelly were arrested on assault charges. She was arrested on suspicion of drunken driving in June of this year. She also divorced her husband that same month for irreconcilable differences.