SALEM, ORE., JULY 11 -- A former surrogate mother who was serving a life sentence for shooting to death one of her three children and wounding two others escaped today from the Oregon State Women's Correctional Center, officials said.

Robey Eldridge, spokesman for the Oregon Corrections Division, said Elizabeth Diane Downs climbed a 20-foot fence surrounding the women's prison and hitched a ride on a street in front of the facility.

Oregon State Police searched for Downs with a plane while patrols combed the streets and fields near the prison adjacent to the Oregon State Penitentiary in Salem.

Downs, 31, entered the prison on Aug. 31, 1984, after being sentenced to life plus 50 years. She was convicted in Lane County Circuit Court for the May 19, 1983, shooting death of Cheryl Lynn Downs, 7, and wounding Christie Ann Downs, now 12, and Stephen (Danny) Downs, now 7.

Downs said the children were shot by a shaggy-haired stranger who flagged down her car on a country road outside Springfield, but the prosecution argued that Downs, who was divorced, shot her children in her car because they were hindering her relationship with a boyfriend. Her convictions have been upheld by the Oregon Court of Appeals and the Oregon Supreme Court.

Downs, who became a surrogate mother under a $10,000 contract on May 8, 1982, bore a baby girl as a result of artificial insemination. She indicated at the time that she did so in part to make up for having had an abortion.

Soon after Downs was imprisoned in June 1984, she gave birth to a girl, Charity Lynn. Oregon took custody of the child.

Eldridge said a nurse on her way to work saw a woman under a truck in the prison parking lot. He said the nurse watched the woman crawl from under the truck and run toward a street in front of the prison.

The nurse informed prison officials, who conducted a check of inmates and determined that Downs was missing, Eldridge said.

He said Downs was picked up by a car that drove westbound and that she was seen getting out of the car a few blocks from the prison.