SEATTLE -- The man suspected of being the Green River Killer has agreed to plead guilty next week to the murders of 48 women in a deal that would spare him from execution, a source told The Associated Press on Thursday.

Gary Leon Ridgway, a 54-year-old truck painter arrested in the serial killer case in 2001, will admit to murdering 42 women on investigators' list of Green River Killer victims, as well as six women not on the list, said the source, speaking on condition of anonymity.

The Green River Killer preyed mostly on prostitutes, drug addicts, young runaways and other women on the streets. The case is named for the waterway where the first bodies were found in the suburbs south of Seattle in mid-1982. Most of the slayings were in the mid-1980s, but one of the slayings to which Ridgway will plead guilty was in 1998, the source said.

In many cases, the killer had sex with his victim and then strangled her.

Ridgway was arrested nearly two years ago and was ultimately charged with seven slayings. Prosecutors said DNA evidence and microscopic paint particles linked him to most of those killings.

Seattle-area newspapers and TV stations had been reporting the possibility of a plea bargain over the past few days.

With the death penalty off the table, Ridgway would face life in prison without parole -- the only other penalty for aggravated murder under Washington law.

Detective Kathleen Larson, a spokeswoman for the Green River Killer task force, would not comment when contacted by the AP on Wednesday and Thursday.

The women Ridgway will admit killing who were not on the list include Patricia Ann Yellow Robe, 38, of Seattle, a nurse's aide who was found dead by a wrecking crew in 1998.

"I guess I'm a little stunned, you know," said her father, Joe Yellow Robe of Box Elder, Mont., told KING-TV. "I find it incredible that an individual was able to cause that many deaths, to perpetrate that much suffering and misery on so many people."

Task force detectives have found four sets of human remains at various sites in recent months. That led to speculation that Ridgway himself was directing investigators to the burial sites.