Heather O'Rourke, the terrified youngster sucked into a spectral vacuum by supernatural spirits in the "Poltergeist" films, has died on an operating table at a San Diego hospital, it was reported Tuesday.

The 12-year-old ingenue, who finished filming "Poltergeist III" last June in which she starred as the angelic Carol Ann Freeling for the third time, died late Monday afternoon.

A spokeswoman for Children's Hospital of San Diego identified the cause of death as intestinal stenosis--a severe bowel obstruction that the girl evidently had from birth. The obstruction caused an infection that, in turn, brought on septic shock. The shock prompted full cardiac and pulmonary arrest, the spokeswoman said.

Her agent, David Wardlowe, said she had been rushed to the hospital after complaining of abdominal pain.

Heather's parents, who live in Big Bear but are also believed to have a home in San Diego, were too distraught to comment, Wardlowe said.

Ron Pennington, a spokesman for Metro-Goldwyn-Mayer Pictures Inc., where the "Poltergeist" films were produced starting in 1981, said the studio "extends its sympathy to her parents and family."

What proved to be her final film will be released this summer, he added.

Heather, who was also seen regularly on television's "Happy Days," "Webster" and "Still the Beaver," brought two catch phrases into the language with the first two "Poltergeists." The first was, "They're heeeere!" which she said with eerie calm after coming into contact with strange forces while peering into an apparently blank TV screen. The second was, "They're baaaack!" which was featured in the sequel.

The "Poltergeist" films, first released in 1982, told of a mid-America family living an idyllic life in the suburbs, whose young daughter begins communing with creatures she sees on her television screen, but only after regular programming ends and the screen has become a series of eerie dots.

Soon family pets begin to die and trees, blown by hurricane-force winds, come smashing into the home of the terrified Freeling family.

Carol Ann is sucked into a light source coming from a closet, and her helpless parents are left only with her screams.

Finally the family turns to a parapsychologist to exorcise the demons.

Heather came to films in a tradition that dates back to Lana Turner when that actress was supposedly (but wasn't really) discovered at a drugstore counter.

Spielberg's Discovery

Heather was 5 and sitting in the MGM commissary, said her former manager, Mike Meyer. Steven Spielberg, who co-wrote and produced the first of the "Poltergeist" series, saw her and asked if he could talk to her. He was told that she did not talk to strangers.

But she got permission, and that eventually led to her role in the film.

Heather is the second actress from the "Poltergeist" movies to die young. Dominique Dunne was strangled in October, 1982.

Miss Dunne, then 22, who played Heather's older sister, had tried to break off her relationship with her boyfriend. Los Angeles chef John Sweeney was convicted of voluntary manslaughter and sentenced in November, 1983, to the maximum 6 1/2 years in prison.

Heather "always looked like 'Alice in Wonderland' and could memorize a 60-page script in about an hour," Meyer said.

"Of all the things she was proud of," he added, "(she was proudest of) being elected president of her fifth grade class at Big Bear Elementary School."

Heather Michele O'Rourke