A 40-year-old woman remained in critical condition Saturday after being attacked by a 500-pound tiger, apparently being playful, during the filming of a television commercial, authorities said.

Clara Frobig, a horse trainer who volunteered to help on a Boeing Co. film Friday, underwent surgery at Evergreen Hospital in Kirkland after the mauling, said a hospital spokeswoman."We first listed her as serious but stable," said spokeswoman Lori McCarthy, "but her wounds turned out to be worse than first thought, partly because of the swelling."

Frobig was bitten severely in the neck and head when she tripped and fell near the animal.