Marilyn Chambers, adult-film star

LOS ANGELES - Marilyn Chambers, 56, the pretty Ivory Snow soap girl who helped bring hard-core adult films into mainstream consciousness when she starred in the explicit 1972 movie

Behind the Green Door

, has died.

The cause of death was not immediately known. A family friend, Peggy McGinn, said Ms. Chambers' 17-year-old daughter found the actress' body Sunday night. Ms. Chambers was pronounced dead at the scene, the county coroner's office said yesterday.

Ms. Chambers and fellow actresses Linda Lovelace and Georgina Spelvin shot to fame at a time in the early 1970s when both American social mores and the quality of hard-core sex films were changing.

For the first time, films like Behind the Green Door and Deep Throat (also released in 1972 and starring Lovelace) had decent acting and legitimate, if fairly thin, plots.

But Behind the Green Door brought something more in Ms. Chambers, an attractive young woman who had begun her career as a legitimate actress and model.

While the film was still in theaters, the public learned that its star was the same young blonde smiling and holding a freshly diapered baby on boxes of Ivory Soap. The manufacturer quickly replaced her, but it was later discovered that she also had a small role in the 1970 Barbra Streisand film The Owl and the Pussycat.

"She was the first crossover adult star. She was the Ivory Snow girl, and when she decided to make an adult movie, that was big news," Steven Hirsch, co-CEO of the adult filmmaker Vivid Entertainment Group, said yesterday.

"She was an actress and she brought that ability to the set of Behind the Green Door. That's part of what made that movie so successful."

She followed Green Door with the hard-core films Resurrection of Eve in 1973 and Inside Marilyn Chambers in 1975.

Then she announced in 1976 that she was giving up adult films to pursue other interests. She starred in the 1977 horror movie Rabid and put together a song-and-dance show that played Las Vegas and elsewhere.

She returned to adult films in 1980 in Insatiable and through the rest of her career went back and forth between explicit and R-rated movies.