Aug. 26, 2011 -- The war of words among the family of missing Utah mother Susan Powell is escalating as the investigation into her disappearance moves into Washington state with police executing a search warrant on the house now occupied by her husband and father-in-law.

Powell's sister-in-law Jennifer Graves called claims of a flirtatious and sexually charged relationship made by her father Steven Powell between him and Susan "slander," and called for a return of focus on the search for the missing mom.

"My dad is saying all kinds of things about Susan that aren't true -- Susan wasn't like this. Steven Powell is," Graves said. "At this point we need to focus on the investigation. All the slander is not helping to find Susan -- we need to go back to an investigation mode instead of a mudslinging mode.

"[Susan's husband] Josh and my dad have done nothing to help, they've done a lot of talking but it's nothing to help find Susan. They're not talking to police. It doesn't portray a man who wants to find his wife," she added.

Meanwhile, 20 detectives are searching the home in Puyallup, Wash. where Powell's 35-year-old husband, Josh Powell, is now living with his father, Steven Powell, along with the couple's two young sons, Charlie and Braden. Josh Powell moved with his boys in to his father's home here after his wife vanished in December 2009.

Half of the investigators executing the search are with the Pierce County, Wash., sheriff and the others are with the West Valley City Police Department in Utah.

At least three computers and four boxes of material were removed from the home by detectives, according to ABC News Seattle affiliate KOMO.

"We came here to look for a few things, and we found a lot of the things we were looking for," said Lt. Bill Merritt.

Josh Powell was at home when investigators arrived and is not being detained. Pierce County sheriff's spokesman Ed Troyer. Crime scene tape surrounded the house while it was searched; Charlie and Braden Powell ate pizza as they played in the house's back yard.

It is also believed that investigators are searching for journals from Susan Powell's teenage years.

Steven Powell said that he plans to post his daughter-in-law's teenage journals on the website SusanPowell.org; according to the Salt Lake Tribune, he says that the journals show that his daughter-in-law is capable of walking out on her husband and their two sons. He has publicly theorized that she disappeared with a man from St. George, Utah, who disappeared from a Christmas party abruptly the same night she vanished.

The search of their home began the same day that both father and son appeared on "Good Morning America" to discuss their relationship with Susan Powell. In the interview Steven Powell made new claims that he had a flirtatious relationship with his daughter-in-law that was "a little beyond the pale."

"Father-in-law - daughter-in-law flirting with each other, maybe some sexual touching or whatever," Steven Powell said of the relationship that he developed with his son's wife, adding that he started to fall in love with her, and stated "there's no question in my mind that the feelings were mutual."

Jennifer Graves' sentiment was similar to that of Chuck Cox, Susan Powell's father. When interviewed on "Good Morning America" on Thursday, Cox refuted Steven Powell's claims that his daughter and her husband's father were in love and that she was flirtatious towards her father-in-law.

"That's completely false and I am very very surprised that he would come out with this type of accusation," Cox said. "I have been aware of my daughter's problems with Steven Powell -- she had told us a long time ago that he had made some advances toward her … told us that it made her uncomfortable, and that her husband didn't care. They decided to move to Utah and that was to get away from Steven."

Josh Powell also described his wife as flirtatious and mentally unstable when interviewed on "Good Morning America." He recounted an instance of her leaving the house in only her underwear, and described what he called a troubled childhood.

"Susan was very -- emotionally abused as a child. Her mother has some very … she has a very angry personality. Her father is very manipulative," he said.

When told of his father's revelation that he had a flirtatious and sexually charged relationship with his daughter-in-law -- and that it was typically initiated by her -- Josh Powell denied it, but also said that any flirtation has to do with his wife's nature.

"There was nothing like that. She's a very flirtatious person. But that's just her personality. You know, it's -- it's part of her friendliness," he said.

While he has not been arrested or charged in her disappearance, police said he continues to be considered a person of interest. He maintains his innocence.

"Everyone who knows me knows that I would never hurt her and I would never hurt my boys," Powell said. "I would never hurt anyone."