SALT LAKE CITY — Investigators found child pornography on Josh Powell’s computer at least 17 months before he killed his children and himself, according to FBI documents obtained by The Salt Lake Tribune.

The paper reported Saturday that documents show the FBI was investigating Powell in the disappearance of his wife, Susan Powell, who was last seen at her West Valley City, Utah, home on Dec. 6, 2009, as well as for possession of child pornography.

Anne Bremner, an attorney for Susan Powell’s parents, said the family was never told the FBI was investigating Josh Powell for child pornography. If the state of Washington’s Department of Social and Health Services had known about the suspected child pornography, Bremner said, it “never would have let him have those kids.”

When a state worker delivered 7-year-old Charlie and 5-year-old Braden to Josh Powell’s rented home in Graham, Pierce County, on Feb. 5, 2012, Josh Powell locked out the worker and ignited a fire that killed him and his sons.

Powell for years had been considered a person of interest in his wife’s disappearance, and eventually he moved back to the Puyallup area, where both his father and his wife’s parents lived.

He lost custody of the boys after his father was arrested for possessing child pornography in another house they previously shared. The boys were in the custody of the state, but living with Susan Powell’s parents. However, Josh Powell was allowed supervised visitation.

Shortly before their deaths, Charlie and Braden Powell had begun talking to their grandparents about things they remembered from the night their mother vanished, a lawyer for the grandparents has said.

On the day of the fire, a state contract worker from Foster Care Resource Network brought the boys for a visit to Powell’s house. Powell answered the door, pulled the boys inside, slammed the door and locked it. The caseworker banged on doors and windows and called 911, but soon smelled gasoline and the fire erupted.

Josh Powell had been previously linked to child pornography, The Tribune reported. At hearings in Washington state to determine custody of his children, then-Assistant Washington Attorney General John M. Long said Powell was under investigation for child pornography after cartoon images of incest between mothers and children were found on his computer in late 2009 or early 2010.

The paper reported that the FBI appeared to be trying to discover what other images might be on Josh Powell’s computer, but the machine had been successfully encrypted by Powell.

Last month, a federal judge ruled that insurance proceeds from the fatal fire could be split between Josh Powell’s parents and sister and Susan Powell’s family.