The two boys reportedly have since been taken into protective custody by Washington state child welfare officials.
West Valley City police who reviewed seized videotapes and CDs, which were reportedly taken from Steven Powell's bedroom during the Aug. 25 raid, "found thousands of images of females being videotaped without their knowledge, including Susan Powell. The photographer focuses on the women's buttocks, breasts, and genital areas. Many images were of minor females," Prosecutor Mark Lindquist said in a statement released to The Associated Press.
The images included shots of two girls who were as young as 8 and 10 years old at the time of the recording, the prosecutor said.
Pierce County Sheriff's officials determined those girls lived next door to Steven Powell from June 2006 to August 2007, according to the statement.
His bedroom window faces the side of the victims' residence and the line of sight matches the camera angle seen in the photos, Lindquist said.
Troyer told the newspaper that the photos focused on victims' "intimate parts" and were taken in public or through windows with a telephoto lens, the newspaper reported. Some of the victims were photographed nude, the newspaper reported.
West Valley City investigators turned the evidence over to Pierce County when they discovered it while reviewing the evidence, the newspaper said.
West Valley City police, in a news release sent about 10:30 p.m., confirmed the arrest stemmed from an investigation by the Pierce County Sheriff's Office into evidence seized during the search at Steven Powell's home. The Pierce County Sheriff's Office reported Steven Powell was taken into custody about 10:45 p.m. MST.
The charges are felonies with a standard maximum penalty upon conviction of five years in prison, the Associated Press reported.
While West Valley police maintained the charges had no direct connect to Susan Powell's disappearance. However, Steven Powell's estranged daughter, Jennifer Graves of West Jordan, indicated her father's arrest and the allegations against him made her increasingly suspicious of her father's possible involvement in Susan Powell's case.
He could be "responsible or helped things along," she told KSL News in an interview aired Friday morning.
Graves said she both laughed and cried when she learned of her father's arrest. She did not know he may have been taking inappropriate pictures, she said, but was aware that "he definitely collected magazines and things" of a sexual nature.
"He's got a pretty sick problem there," Graves said, adding that she was relieved to have learned her two nephews were removed from their grandfather's home. "I know my dad's character," she said.
The boys have been sharing Steven Powell's home along with their father, Josh Powell, the only person of interest police have named in his wife's disappearance.
On Thursday, West Valley City investigators continued to comb the desert near Topaz Mountain in Juab County searching for Susan Powell.
Josh Powell says he took his two young sons camping Dec. 6, 2009, the night his wife disappeared from their West Valley City home.