Actress Lisa Robin Kelly, best known for her supporting role on the popular Fox television comedy That '70s Show, has died at age 43, days after checking into a treatment facility for substance abuse, her agent said on Thursday.

The blonde actress co-starred in about 50 episodes of the series, which ran from 1998 to 2003, as the attractive, promiscuous Laurie Forman, the older, college-age sister of the lead character, Eric Forman, played by Topher Grace.

Dead at 43: Lisa Robin Kelly, centre, was among the widely reknown cast of That '70s Show.

Kelly left the series in the sixth season, replaced by actress Christina Moore.

According to her agent, Craig Wyckoff, Kelly died on Wednesday evening at the facility.