MERCED, Calif. -- A convicted murderer serving a life sentence in Montana was given two more life sentences after pleading guilty to two murders, prosecutors said Tuesday.

Ronald James Ward Jr., 42, was given the two life sentences without the possibility of parole after pleading guilty to killing Shela Polly of Modesto and Jacquelyn Travis of Merced, prosecutors said.

Ward was the prime suspect in a 2006 killing, and is also connected to three other homicides stretching from Merced to Arkansas.

He was already convicted and serving a life-term for a murder in Montana, but agreed to come to California to be arraigned in the valley killings.

"This ensures that this depraved individual will never see the light of day as a free man," Stanislaus County District attorney Birgit Fladager said.

Prosecutors said they think Ward may have more victims whose bodies have not been discovered yet.

"We believe it highly unlikely that Ronald Ward started and stopped killing in 2000," District Attorney Larry Morse said.

Polly's 11-year-old daughter read a statement in the courtroom Tuesday to Ward.

Ward will be brought back to custody in Montana, prosecutors said.